Graves Disease

Background

Graves disease, named after Robert J. Graves, MD,^[1] circa 1830s, is an autoimmune disease characterized by hyperthyroidism due to circulating autoantibodies. Thyroid-stimulating immunoglobulins (TSIs) bind to and activate thyrotropin receptors, causing the thyroid gland to grow and the thyroid follicles to increase synthesis of thyroid hormone. Graves disease, along with Hashimoto thyroiditis, is classified as an autoimmune thyroid disorder.

In some patients, Graves disease represents a part of more extensive autoimmune processes leading to dysfunction of multiple organs (eg, polyglandular autoimmune syndromes). Graves disease is associated with pernicious anemia, vitiligo, diabetes mellitus type 1, autoimmune adrenal insufficiency, systemic sclerosis, myasthenia gravis, Sjögren syndrome, rheumatoid arthritis, and systemic lupus erythematosus.^[2]

Graves ophthalmopathy is shown below.

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Graves disease. Varying degrees of manifestations of Graves ophthalmopathy.

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Pathophysiology

In Graves disease, B and T lymphocyte-mediated autoimmunity are known to be directed at 4 well-known thyroid antigens: thyroglobulin, thyroid peroxidase, sodium-iodide symporter and the thyrotropin receptor. However, the thyrotropin receptor itself is the primary autoantigen of Graves disease and is responsible for the manifestation of hyperthyroidism. In this disease, the antibody and cell-mediated thyroid antigen-specific immune responses are well defined. Direct proof of an autoimmune disorder that is mediated by autoantibodies is the development of hyperthyroidism in healthy subjects by transferring thyrotropin receptor antibodies in serum from patients with Graves disease and the passive transfer of thyrotropin receptor antibodies to the fetus in pregnant women.

The thyroid gland is under continuous stimulation by circulating autoantibodies against the thyrotropin receptor, and pituitary thyrotropin secretion is suppressed because of the increased production of thyroid hormones. The stimulating activity of thyrotropin receptor antibodies is found mostly in the immunoglobulin G1 subclass. These thyroid-stimulating antibodies cause release of thyroid hormone and thyroglobulin that is mediated by 3,'5'-cyclic adenosine monophosphate (cyclic AMP), and they also stimulate iodine uptake, protein synthesis, and thyroid gland growth.

The anti-sodium-iodide symporter, antithyroglobulin, and antithyroid peroxidase antibodies appear to have little role in the etiology of hyperthyroidism in Graves disease. However, they are markers of autoimmune disease against the thyroid. Intrathyroidal lymphocytic infiltration is the initial histologic abnormality in persons with autoimmune thyroid disease and can be correlated with the titer of thyroid antibodies. Besides being the source of autoantigens, the thyroid cells express molecules that mediate T cell adhesion and complement regulation (Fas and cytokines) that participate and interact with the immune system. In these patients, the proportion of CD4 lymphocytes is lower in the thyroid than in the peripheral blood. The increased Fas expression in intrathyroidal CD4 T lymphocytes may be the cause of CD4 lymphocyte reduction in these individuals.

Several autoimmune thyroid disease susceptibility genes have been identified: CD40, CTLA-4, thyroglobulin, TSH receptor, and PTPN22.^{[3, 4]} Some of these susceptibility genes are specific to either Graves disease or Hashimoto thyroiditis, while others confer susceptibility to both conditions. The genetic predisposition to thyroid autoimmunity may interact with environmental factors or events to precipitate the onset of Graves disease.

Two new susceptibility loci were found: the RNASET2-FGFR1OP-CCR6 region at 6q27 and an intergenic region at 4p14.^[5] Moreover, strong associations of thyroid-stimulating hormone receptor and major histocompatibility complex class II variants with persistently thyroid stimulating hormone receptor autoantibodies (TRAb)-positive Graves disease were found.^[6]

Graves disease patients a have higher rate of peripheral blood mononuclear cell conversion into CD34⁺ fibrocytes compared with healthy controls. These cells may contribute to the pathophysiology of ophthalmopathy by accumulating in orbital tissues and producing inflammatory cytokines, including TNF-alpha and IL-6.^[7] In a genome-wide association study of more than 1500 Graves disease patients and 1500 controls, 6 susceptibility loci were found to be related to Graves disease (major histocompatibility complex, TSH receptor, CTLA4, FCRL3, RNASET2-FGFR1OP-CCR6 region at 6q27, and an intergenic region at 4p14.^[8]

Pathophysiologic mechanisms are shown in the image below.

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Pathophysiologic mechanisms of Graves disease relating thyroid-stimulating immunoglobulins to hyperthyroidism and ophthalmopathy. T4 is levothyroxine.....

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Epidemiology

Frequency

United States

Graves disease is the most common cause of hyperthyroidism in the United States. A study conducted in Olmstead County, Minnesota estimated the incidence to be approximately 30 cases per 100,000 persons per year.^[9] The prevalence of maternal thyrotoxicosis is approximately 1 case per 500 persons, with maternal Graves disease being the most common etiology. Commonly, patients have a family history involving a wide spectrum of autoimmune thyroid diseases, such as Graves disease, Hashimoto thyroiditis, or postpartum thyroiditis, among others.

International

Among the causes of spontaneous thyrotoxicosis, Graves disease is the most common. Graves disease represents 60-90% of all causes of thyrotoxicosis in different regions of the world. In the Wickham Study in the United Kingdom, the incidence was reported to be 100-200 cases per 100,000 population per year.^[10] The incidence in women in the UK has been reported to be 80 cases 100,000 per year.^[11]

Mortality/Morbidity

If left untreated, Graves disease can cause severe thyrotoxicosis. A life-threatening thyrotoxic crisis (ie, thyroid storm) can occur. Long-standing severe thyrotoxicosis leads to severe weight loss with catabolism of bone and muscle.^[12] Cardiac complications and psychocognitive complications can cause significant morbidity. Graves disease is also associated with ophthalmopathy, dermopathy, and acropachy.

Thyroid storm is an exaggerated state of thyrotoxicosis.^[13] It occurs in patients who have unrecognized or inadequately treated thyrotoxicosis and a superimposed precipitating event such as thyroid surgery, nonthyroidal surgery, infection, or trauma. When thyroid storm was first described, the acute mortality rate was nearly 100%. In current practice, with aggressive therapy and early recognition of the syndrome, the mortality rate is approximately 20%.^[14]

Long-term excess of thyroid hormone can lead to osteoporosis in men and women. The effect can be particularly devastating in women, in whom the disease may compound the bone loss secondary to chronic anovulation or menopause. Bone loss is accelerated in patients with hyperthyroidism. The increase in bone loss can be demonstrated by increased urinary pyridinoline cross-link excretion. Serum calcium and phosphate, plasma FGF-23 were significantly higher in the patients with Graves disease than in healthy control subjects, suggesting that FGF-23 is physiologically related to serum phosphate homeostasis in untreated Graves disease.^[15]

Hyperthyroidism increases muscular energy expenditure and muscle protein breakdown. These abnormalities may explain the sarcopenia and myopathy observed in patients with hyperthyroid Graves disease.

Cardiac hypertrophy has been reported in thyrotoxicosis of different etiologies. Rhythm disturbances such as extrasystolic arrhythmia, atrial fibrillation, and flutter are common. Cardiomyopathy and congestive heart failure can occur.^[16]

Psychiatric manifestations such as mood and anxiety disorders are common.^[17] Subjective cognitive dysfunction is often reported by Graves disease patients and may be due to affective and somatic manifestations of thyrotoxicosis, which remit after treatment of Graves thyrotoxicosis.^[18]

Nonpitting edema is the most prevalent form of dermopathy (about 40%) and are primarily in the pretibial area. The nearly all (>95%) patients with dermopathy had ophthalmopathy.^[19] Advanced forms of dermopathy are elephantiasis or thyroid acropachy. Severe acropachy can be disabling and can lead to total loss of hand function.

Progression of ophthalmopathy can lead to compromised vision and blindness. Visual loss due to corneal lesions or optic nerve compression can be seen in severe Graves ophthalmopathy.

In a study of 1128 patients with Graves ophthalmopathy, Kim et al found the prevalence of ocular hypertension (OHT) to be 6.8% and the prevalence of open-angle glaucoma (OAG) to be 1.6%. The prevalences were higher in patients over age 40 years, being 9.5% and 3.4%, respectively. The investigators also reported the prevalence of OHT in Graves ophthalmopathy to be associated with male sex, duration of the ophthalmopathy, a clinical activity score of 3 or above, extraocular muscle involvement, and lid retraction. Male sex and duration of the ophthalmopathy were associated with the prevalence of OAG in Graves ophthalmopathy.^[20]

Maternal Graves disease can lead to neonatal hyperthyroidism by transplacental transfer of thyroid-stimulating antibodies. Approximately 1-5% of children of mothers with Graves disease (usually with high TSI titer) are affected. Usually, the TSI titer falls during pregnancy.

Elderly individuals may develop apathetic hyperthyroidism, and the only presenting features may be unexplained weight loss or cardiac symptoms such as atrial fibrillation and congestive heart failure.

Boelaert et al investigated the prevalence of and relative risks for coexisting autoimmune diseases in patients with Graves disease (2791 patients) or Hashimoto thyroiditis (495 patients). The authors found coexisting disorders in 9.7% of patients with Graves disease and in 14.3% of those with Hashimoto thyroiditis, with rheumatoid arthritis being the most common of these (prevalence = 3.15% and 4.24% in Graves disease and Hashimoto thyroiditis, respectively). Relative risks of greater than 10 were found for pernicious anemia, systemic lupus erythematosus, Addison disease, celiac disease, and vitiligo. The authors also reported a tendency for parents of patients with Graves disease or Hashimoto thyroiditis to have a history of hyperthyroidism or hypothyroidism, respectively.^[21]

Race

In whites, autoimmune thyroid diseases are, based on linkage analysis, linked with the following loci: AITD1, CTLA4, GD1, GD2, GD3, HT1, and HT2. Different loci have been reported to be linked with autoimmune thyroid diseases in persons of other races.

Susceptibility is influenced by genes in the human leukocyte antigen (HLA) region on chromosome 6 and in CTLA4 on band 2q33. Association with specific HLA haplotypes has been observed and is found to vary with ethnicity.

Sex

As with most autoimmune diseases, susceptibility is increased in females. Hyperthyroidism due to Graves disease has a female-to-male ratio of 7-8:1.

The female-to-male ratio for pretibial myxedema is 3.5:1. Only 7% of patients with localized myxedema have thyroid acropachy.

Unlike the other manifestations of Graves disease, the female-to-male ratio for thyroid acropachy is 1:1.

Age

Typically, Graves disease is a disease of young women, but it may occur in persons of any age.

The typical age range is 20-40 years.

Most affected women are aged 30-60 years.

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Prognosis

The natural history of Graves disease is that most patients become hypothyroid and require replacement. Similarly, the ophthalmopathy generally becomes quiescent. On occasion, hyperthyroidism returns because of persisting thyroid tissue after ablation and high antibody titers of anti-TSI. Further therapy may be necessary in the form of surgery or radioactive iodine ablation.

A study by Tun et al indicated that in patients with Graves disease receiving thionamide therapy, high thyrotropin receptor–stimulating antibody (TRab) levels at diagnosis of the disease and/or high TRab levels at treatment cessation are risk factors for relapse, particularly within the first two years. The study included 266 patients.^[22]

A retrospective study by Rabon et al indicated that in children with Graves disease, antithyroid drugs usually do not induce remission, although most children who do achieve remission through these agents do not relapse. Of 268 children who were started on an antithyroid drug, 57 (21%) experienced remission, with 16 of them (28%) relapsing.^[23]

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Patient Education

Awareness of the symptoms related to hyperthyroidism and hypothyroidism is important, especially in the titration of antithyroid agents and in replacement therapy for hypothyroidism.

Patients also should be aware of the potential adverse effects of these medicines. They should watch for fever, sore throat, and throat ulcers.

Patients also must be instructed to avoid cold medicines that contain alpha-adrenergic agonists such as ephedrine or pseudoephedrine.

For patient education resources, see the Endocrine System Center, as well as Thyroid Problems.

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History

Because Graves disease is an autoimmune disorder that also affects other organ systems, taking a careful patient history is essential to establishing the diagnosis.

In some cases, the history might suggest a triggering factor such as trauma to the thyroid, including surgery of the thyroid gland, percutaneous injection of ethanol, and infarction of a thyroid adenoma. Other factors might include interferon (eg, interferon beta-1b) or interleukin (IL-4) therapy.

Patients usually present with symptoms typical of thyrotoxicosis. Hyperthyroidism is characterized by both increased sympathetic and decreased vagal modulation.^[24] Tachycardia and palpitation are very common symptoms.

Not all patients present with such classic features. In fact, a subset of patients with euthyroid Graves disease is described.

In elderly individuals, fewer symptoms are apparent to the patient. Clues may include unexplained weight loss, hyperhidrosis, or rapid heart beat.

Young adults of Southeast Asian descent may complain of sudden paralysis thought to be related to thyrotoxic periodic paralysis. There is an association of polymorphisms of the calcium channel alpha1-subunit gene with thyrotoxic periodic paralysis.^[25] One third of patients with thyrotoxic hypokalemic periodic paralysis were found to have mutations in the inwardly rectifying potassium channel (Kir2.6).^[26]

The symptoms of Graves disease, organized by systems, are as follows:

• General - Fatigue, general weakness
• Dermatologic - Warm, moist, fine skin; sweating; fine hair; onycholysis; vitiligo; alopecia; pretibial myxedema
• Neuromuscular - Tremors, proximal muscle weakness, easy fatigability, periodic paralysis in persons of susceptible ethnic groups
• Skeletal - Back pain, increased risk for fractures
• Cardiovascular - Palpitations, dyspnea on exertion, chest pain, edema
• Respiratory - Dyspnea
• Gastrointestinal - Increased bowel motility with increased frequency of bowel movements
• Ophthalmologic - Tearing, gritty sensation in the eye, photophobia, eye pain, protruding eye, diplopia, visual loss
• Renal - Polyuria, polydipsia
• Hematologic - Easy bruising
• Metabolic - Heat intolerance, weight loss despite increase or similar appetite, worsening diabetes control
• Endocrine/reproductive - Irregular menstrual periods, decreased menstrual volume, secondary amenorrhea, gynecomastia, impotence
• Psychiatric - Restlessness, anxiety, irritability, insomnia

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Physical

Most of the physical findings are related to thyrotoxicosis.

Physical findings that are unique to Graves disease but not associated with other causes of hyperthyroidism include ophthalmopathy and dermopathy. Myxedematous changes of the skin (usually in the pretibial areas) are described as resembling an orange peel in color and texture. Onycholysis can be seen usually in the fourth and fifth fingernails.

The presence of a diffusely enlarged thyroid gland, thyrotoxic signs and symptoms, together with evidence of ophthalmopathy or dermopathy, can establish the diagnosis.

Common physical findings, organized by anatomic regions, are as follows:

• General - Increased basal metabolic rate, weight loss despite increase or similar appetite
• Skin - Warm, most, fine skin; increased sweating; fine hair; vitiligo; alopecia; pretibial myxedema
• Head, eyes, ears, nose, and throat - Chemosis, conjunctival irritation, widening of the palpebral fissures, lid lag, lid retraction, proptosis, impairment of extraocular motion, visual loss in severe optic nerve involvement, periorbital edema
• Neck - Upon careful examination, the thyroid gland generally is diffusely enlarged and smooth; a well-delineated pyramidal lobe may be appreciated upon careful palpation; thyroid bruits and, rarely, thrills may be appreciated; thyroid nodules may be palpable.
• Chest - Gynecomastia, tachypnea, tachycardia, murmur, hyperdynamic precordium, S3, S4 heart sounds, ectopic beats, irregular heart rate and rhythm
• Abdomen - Hyperactive bowel sound
• Extremities - Edema, acropachy, onycholysis
• Neurologic - Hand tremor (fine and usually bilateral), hyperactive deep tendon reflexes
• Musculoskeletal - Kyphosis, lordosis, loss of height, proximal muscle weakness, hypokalemic periodic paralysis in persons of susceptible ethnic groups
• Psychiatric - Restlessness, anxiety, irritability, insomnia, depression

Ophthalmopathy is a hallmark of Graves disease. Approximately 25-30% of patients with Graves disease have clinical evidence of Graves ophthalmopathy. Progression from mild to moderate/severe ophthalmopathy occurs in about 3% of cases.^[27] Thyrotropin receptor is highly expressed in the fat and connective tissue of patients with Graves ophthalmopathy. Measuring diplopia fields, eyelid fissures, range of extraocular muscles, visual acuity, and proptosis provides quantitative assessment to follow the course of ophthalmopathy. Signs of corneal or conjunctival irritation include conjunctival injection and chemosis. A complete ophthalmologic examination, including retinal examination and slit-lamp examination by an ophthalmologist, is indicated if the patient is symptomatic.

Although thyroid nodule(s) may be present, excluding multinodular toxic goiter (especially in older patients) as the cause of thyrotoxicosis is essential. The approach to treatment may be different. Excluding thyroid neoplasia is also important in these patients because reports have indicated that differentiated thyroid cancer is probably more common in patients with Graves disease and may also have a more aggressive course in these patients.^[28]

Similarly, mortality has been reported to be increased in patients with Graves disease and differentiated thyroid carcinoma compared with euthyroid control patients with differentiated thyroid carcinoma.^[29] Graves disease patients had also higher mortality rates compared with general population, with a particular increase in mortality due to cardiovascular and lung disorders, while hyperthyroid patients had increased mortality secondary to toxic nodules had increased mortality associated with malignancies.^[30]

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Causes

Graves disease is autoimmune in etiology, and the immune mechanisms involved may be one of the following:

• Expression of a viral antigen (self-antigen) or a previously hidden antigen
• The specificity crossover between different cell antigens with an infectious agent or a superantigen
• Alteration of the T cell repertoire, idiotypic antibodies becoming pathogenic antibodies
• New expression of HLA class II antigens on thyroid epithelial cells (eg, HLA-DR antigen)

The autoimmune process in Graves disease is influenced by a combination of environmental and genetic factors.

Several autoimmune thyroid disease susceptibility genes have been identified: CD40, CTLA-4, thyroglobulin, TSH receptor, and PTPN22.^[3] Some of these susceptibility genes are specific to either Graves disease or Hashimoto thyroiditis, while others confer susceptibility to both conditions. HLA-DRB1 and HLA-DQB1 also appear to be associated with Graves disease susceptibility. Genetic factors contribute approximately 20-30% of overall disease susceptibility.

• Cytotoxic T lymphocyte-associated molecule-4 (CTLA4) is a major thyroid autoantibody susceptibility gene,^{[31, 32]} and it is a negative regulator of T-cell activation and may play an important role in the pathogenesis of Graves disease. The G allele of exon1 +49 A/G single nucleotide polymorphism (SNP) of the CTLA4 gene influences higher TPOAb and TgAb production in patients who are newly diagnosed with Graves disease.^[31] This SNP of the CTLA4 gene can also predict recurrence of Graves disease after cessation of thionamide treatment.^[33]
• There is an association of a C/T SNP in the Kozak sequence of CD40 with Graves disease.^{[3, 34]}
• The association of SNPs in PTPN22 varies among autoimmune diseases individually or as part of a haplotype, and the mechanisms by which PTPN22 confers susceptibility to Graves disease may differ from other autoimmune diseases.^[35]
• Alleles of intron 7 of the thyrotropin receptor gene (TSHR) have also been shown to contribute to susceptibility to Graves disease.
• Inhibitory antibodies directed against insulinlike growth factor receptor-1 (IGFR-1) were seen in 14% of patients with Graves ophthalmopathy, but there was no activation of IGFR-1 in association with these antibodies.^[36]

Environmental factors associated with susceptibility are largely unproven. Other factors include infection, iodide intake, stress, female sex, steroids, and toxins. Smoking has been implicated in the worsening of Graves ophthalmopathy.

• Graves disease has been associated with a variety of infectious agents such as Yersinia enterocolitica and Borrelia burgdorferi. Homologies have been shown between proteins of these organisms and thyroid autoantigens.^{[37, 38]}
• Stress can be a factor for thyroid autoimmunity. Acute stress-induced immunosuppression may be followed by immune system hyperactivity, which could precipitate autoimmune thyroid disease. This may occur during the postpartum period, in which Graves disease may occur 3-9 months after delivery. Estrogen may influence the immune system, particularly the B-cell repertoire. Both T- and B-cell function are diminished during pregnancy, and the rebound from this immunosuppression is thought to contribute to the development of postpartum thyroid syndrome.
• Interferon beta-1b and interleukin-4, when used therapeutically, may cause Graves disease.
• Trauma to the thyroid has also been reported to be associated with Graves disease. This may include surgery of the thyroid gland, percutaneous injection of ethanol, and infarction of a thyroid adenoma.

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Laboratory Studies

Ultrasensitive (third-generation) thyrotropin assays remain the best screening test for thyroid disorders.

• With the exception of thyrotropin-induced hyperthyroidism, subnormal or suppressed thyrotropin levels are seen in most patients with thyrotoxicosis.
• Free T4 levels or the free T4 index is usually elevated, as is the free T3 level or free T3 index. Subclinical hyperthyroidism, defined as a free T4 or free T3 level within the reference range with suppressed thyrotropin, also can be seen.
• On occasion, only the free T3 level is elevated, a syndrome known as T3 toxicosis. This may be associated with toxic nodular goiter or the ingestion of T3. Elevated T3 levels are often seen in early phase Graves disease as well.
• Assays for thyrotropin-receptor antibodies (particularly TSIs) almost always are positive.
• Detection of TSIs is diagnostic for Graves disease.
• The presence of TSIs is particularly useful in reaching the diagnosis in pregnant women, in whom the use of radioisotopes is contraindicated.
• Other markers of thyroid autoimmunity, such as antithyroglobulin antibodies or antithyroidal peroxidase antibodies, are usually present.
• Other autoantibodies that may be present include thyrotropin receptor–blocking antibodies and anti–sodium-iodide symporter antibody.
• The presence of these antibodies supports the diagnosis of an autoimmune thyroid disease.

Liver function test results should be obtained to monitor for liver toxicity caused by thioamides (antithyroid medications).

A CBC count with differential should be obtained at baseline and with the development of fever or symptoms of infection. Graves disease may be associated with normocytic anemia, low-normal to slightly depressed total WBC count with relative lymphocytosis and monocytosis, low-normal to slightly depressed platelet count. Thioamides may rarely cause severe hematologic side effects, but routine screening for these rare events is not cost-effective.

Investigation of gynecomastia associated with Graves disease may reveal increased sex hormone–binding globulin levels and decreased free testosterone levels.

Graves disease may worsen diabetes control and may be reflected by an increase in hemoglobin A1C in diabetic patients.

A fasting lipid profile may show decreased total cholesterol levels and decreased triglyceride levels.

Thyrotropin-releasing hormone testing has largely been replaced by third-generation thyrotropin assays.

A high titer of serum antibodies to collagen XIII is associated with active Graves ophthalmopathy.^[40]

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Imaging Studies

Radioactive iodine scanning and measurements of iodine uptake are useful in differentiating the causes of hyperthyroidism. In Graves disease, the radioactive iodine uptake is increased and the uptake is diffusely distributed over the entire gland.^[39]

Ultrasounds with color-Doppler evaluation have been found to be cost-effective in hyperthyroid patients.^{[28, 41]} A prospective trial showed that thyroid ultrasound findings are predictive of radioiodine treatment outcome, and, in patients with Graves disease, normoechogenic and large glands are associated with increased radioresistance.^[42]

Computed tomography scanning or magnetic resonance imaging (of the orbits) may be necessary in the evaluation of proptosis. If routinely performed, most patients have evidence of ophthalmopathy, such as an increased volume of extraocular muscles and/or retrobulbar connective tissue. These techniques are useful to monitor changes over time or to ascertain the effects of treatment. Careful monitoring is required after using iodinated contrast agents as they may affect ongoing treatment plans.

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Histologic Findings

In select cases in which thyroidectomy was performed for the treatment of severe hyperthyroidism, the thyroid glands from patients with Graves disease show lymphocytic infiltrates and follicular hypertrophy, with little colloid present.

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Medical Care

Treatment involves alleviation of symptoms and correction of the thyrotoxic state. Adrenergic hyperfunction is treated with beta-adrenergic blockade. Correcting the high thyroid hormone levels can be achieved with antithyroid medications that block the synthesis of thyroid hormones or by treatment with radioactive iodine.

A study by Yasuda et al of pediatric patients with Graves disease found that a greater incidence and variety of adverse events occurred in those on a high dose of the antithyroid drug methimazole (0.7 or more mg/kg/day) than in those on a low dose (< 0.7 mg/kg/day), with the frequencies of adverse events being 50% and 20%, respectively. However, neutropenia and rash were found to manifest independently of dose.^[43]

Radioactive iodine

The most commonly used therapy for Graves disease is radioactive iodine. Indications for radioactive iodine over antithyroid agents include a large thyroid gland, multiple symptoms of thyrotoxicosis, high levels of thyroxine, and high titers of TSI. Information and guidelines are as follows:

• Many physicians in the United States prefer to use radioactive iodine as first-line therapy, especially in younger patients, because of the high relapse rate (>50%) associated with antithyroid therapy.
• Radioiodine treatment can be performed in an outpatient setting.
• The usual dose ranges from 5-15 mCi, determined either by using various formulas that take into account the estimated thyroid weight and radioiodine uptake or by using fixed dosages of iodine I 131; detailed kinetic studies of¹³¹ I are not essential and do not lead to better treatment results. A fixed dose of 7 mCi has been advocated by some researchers as the first empirical dose in the treatment of hyperthyroidism. In general, higher dosages are required for patients who have large goiters, have low radioiodine uptake, or who have been pretreated with antithyroid drugs.
• Patients currently taking antithyroid drugs must discontinue the medication at least 2 days prior to taking the radiopharmaceutical.^[44] In one study, withholding antithyroid drugs for just over 2 weeks before radioiodine treatment resulted in the lowest failure rate. Pretreatment with thioamides reduces the cure rate of radioiodine therapy in hyperthyroid diseases.^[45]
• Thyroid function test results generally improve within 6-8 weeks of therapy, but this can be highly variable.
• With radioactive iodine, the desired result is hypothyroidism due to destruction of the gland, which usually occurs 2-3 months after administration.
• Following up with the patient and monitoring thyroid function monthly or as the clinical condition dictates is important.
• When patients become hypothyroid, they require lifelong replacement with thyroid hormone.
• The possibility exists that radioactive iodine can precipitate thyroid storm by releasing thyroid hormones. This risk is higher in elderly and debilitated patients. This problem can be addressed by pretherapy administration with antithyroidal medication such as propylthiouracil (PTU) or methimazole, but antithyroid medication also may decrease the effectiveness of radioiodine, as discussed above.
• If thyroid function does not normalize within 6-12 months of treatment, a second course at a similar or higher dose can be given. Third courses are rarely needed.
• Hypothyroidism may ensue in the first year in up to 90% of patients given higher doses of radioiodine.
• Approximately one third of patients develop transient hypothyroidism. Unless a patient is highly symptomatic, thyroxine replacement may be withheld if hypothyroidism occurs within the first 2 months of therapy. If it persists for longer than 2 months, permanent hypothyroidism is likely and replacement with T4 should be initiated.
• Radiation thyroiditis is rare, but it may occur and exacerbate thyrotoxicosis.
• Long-term follow-up is mandatory for all patients.
• One concern with the use of radioiodine in persons with Graves disease is its controversial potential for exacerbating existing Graves ophthalmopathy. However, the presence of ophthalmopathy should not influence the choice of therapy for hyperthyroidism. If possible in patients with mild progressive ophthalmopathy, institute a course of steroids (prednisone up to 1 mg/kg) for 2-3 months, tapering a few days before radioiodine therapy. For those with no obvious ophthalmopathy, the chances of exacerbation are much lower. In patients with severe Graves ophthalmopathy, treatment of hyperthyroidism and ophthalmopathy should proceed concurrently and independently of each other.
• The absolute contraindication for radioiodine is pregnancy. No evidence of germ-line mutations has been demonstrated from gonadal exposure. The incidence of birth defects or abnormal pregnancies has not increased after radioiodine treatments.^[46] After radioiodine therapy, germinal epithelium and Leydig cell function may change marginally, which may have some clinical significance in male patients with preexisting fertility impairment.^[47]
• Because it is known that low-dose thyroid radiation exposure in children increases the risk of thyroid cancer later in life, larger doses of¹³¹ I are recommended for children.^[48] If patients are aged 6-10 years, ablative doses of¹³¹ I (100-150 mCi/g of thyroid tissue) may be used to prevent the survival of thyroid cells that may be transformed later into malignant cells. In a national database analysis, Graves disease patients had increased risk of developing malignancies (especially in the first 3 y of diagnosis) compared with controls, especially for breast and thyroid cancer.^[49] Detection bias because of Graves disease diagnosis could be a factor for this epidemiological association.

Graves ophthalmopathy

Graves ophthalmopathy can be divided into 2 clinical phases: the inflammatory stage and the fibrotic stage. The inflammatory stage is marked by edema and deposition of glycosaminoglycan in the extraocular muscles. This results in the clinical manifestations of orbital swelling, stare, diplopia, periorbital edema, and, at times, pain. The fibrotic stage is a convalescent phase and may result in further diplopia and lid retraction. Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (b-FGF) levels may be mechanistically involved in Graves ophthalmopathy. Serum VEGF and b-FGF levels were higher in patients with Graves ophthalmopathy than in patients without, and they correlated with ophthalmopathy clinical activity scores.^[50]

In a longitudinal cohort of 8404 adults with newly diagnosed Graves disease, 740 (8.8%) developed ophthalmopathy.^[51] Graves ophthalmopathy improves spontaneously in 64% of patients. Approximately 10-20% of patients have gradual progression of disease over many years, followed by clinical stability. Approximately 2-5% have progressive worsening of the disease, with visual impairment in some.

Radioactive iodine therapy for Graves disease is a risk factor for Graves ophthalmopathy. Cholesterol-lowering drugs of the hydroxymethylglutarate-coenzyme A reductase inhibitor class were associated with a reduced risk of ophthalmopathy.^[51] Ethnic factors are also important for Graves ophthalmopathy after radioactive iodine treatment; Japanese patients are less prone to Graves ophthalmopathy after radioactive iodine.^[52]

Correction of both hyperthyroidism and hypothyroidism is important for the ophthalmopathy. Antithyroid drugs and thyroidectomy do not influence the course of the ophthalmopathy, whereas radioiodine treatment may exacerbate preexisting ophthalmopathy but can be prevented by glucocorticoids. However, Japanese patients may not respond well to prophylactic use of low-dose glucocorticosteroids.^[52] No beneficial effect of glucocorticoid prophylaxis was found in patients without preexisting clinical evidence of ophthalmopathy.^[53] In the long term, thyroid ablation may be beneficial for ophthalmopathy because of the decrease in antigens shared by the thyroid and the orbit in the autoimmune reactions. In general, treatment of hyperthyroidism is associated with an improvement of ophthalmopathy, but hypothyroidism must be avoided because it worsens ophthalmopathy.^{[54, 55, 56]}

For mild-to-moderate ophthalmopathy, local therapeutic measures (eg, artificial tears and ointments, sunglasses, eye patches, nocturnal taping of the eyes, prisms, elevating the head at night) can control symptoms and signs. If the disease is active, the mainstays of therapy are (1) high-dose glucocorticoids,^[57] (2) orbital radiotherapy, (3) both, or (4) orbital decompression.^[58] A meta-analysis has shown that a 3-month course of prednisone (0.4-0.5 mg/kg) reduced the progression of preexisting mild-to-moderate ophthalmopathy.^[53]

For severe or progressive disease, glucocorticoids at 40 mg/d (usual dose) may be tried. The drug should be continued until evidence of improvement and disease stability is observed. The dosage is then tapered over 4-12 weeks. High-dose pulse glucocorticoid therapy has also been used with good results but may be associated with a slightly increased risk of acute liver damage.^[59]

A study by Liao and Huang evaluated the correlation of retrobulbar volume change, resected orbital fat volume, and proptosis reduction after surgical decompression in patients with Graves ophthalmopathy.^[60] Decompression by resecting orbital fat was found to reduce proptosis in patients with disfiguring Graves ophthalmopathy.

If no response to therapy occurs in the inflammatory phase, orbital radiotherapy with or without steroids may be tried. Orbital radiotherapy did not increase the risk for radiation-induced tumors or retinopathy, except in patients with diabetes with possible or definite retinopathy.^[61] Low-dose radiation from various sources (even if not aimed at the eyes) is linked to cataracts, which may be detected only after long term follow-up.^[62] A meta-analysis found better outcome with combining steroids with radiotherapy compared with steroid therapy alone. However, quality-of-life scores were not different between the 2 groups.^[63] Diuretics have a limited effect on the edema caused by venous engorgement of the orbit.

Gamma knife surgery has been attempted with success in a limited number of patients, but further studies are needed to validate this approach.

Surgical management is generally performed in the fibrotic phase, when the patient is euthyroid.

Novel treatments such as somatostatin analogs or intravenous immunoglobulins are under evaluation. Studies with octreotide LAR (long-acting, repeatable) show conflicting or marginal therapeutic benefit for patients with Graves ophthalmopathy.^{[64, 65, 66]} Infliximab, an anti-tumour necrosis factor alpha (TNF-α) antibody, has been reported to successfully treat a case of sight-threatening Graves ophthalmopathy.^[67] Rituximab, anti-CD20 monoclonal antibody, may transiently deplete B-lymphocytes and potentially suppress the active inflammatory phase of Graves ophthalmopathy.^[68] However, clinical data concerning rituximab are still conflicting and controversial.^{[69, 70]} A multicentered prospective pilot study suggests that periocular injection of triamcinolone may reduce diplopia and the size of extraocular muscles in patients with Graves ophthalmopathy of recent onset.^[71] In a prospective randomized trial, pentoxifylline improved symptoms and proptosis in the inactive phase of Graves ophthalmopathy.^[72]

Pretibial myxedema

Some degree of pretibial (localized dermopathy) myxedema is observed in 5-10% of patients, with 1-2% having cosmetically significant lesions. Affected patients tend to have more severe ophthalmopathy than those who are not affected.

It usually manifests as elevated, firm, nonpitting, localized thickening over the lateral aspect of the lower leg, with bilateral involvement. It also may involve the upper extremities.

Milder cases do not require therapy other than treatment of the thyrotoxicosis.

Therapy with topical steroids applied under an occlusive plastic dressing film (eg, Saran Wrap) for 3-10 weeks has been helpful. In severe cases, pulse glucocorticoid therapy may be tried.

Acropachy

Clubbing of fingers with osteoarthropathy, including periosteal new bone formation, may occur. This almost always occurs in association with ophthalmopathy and dermopathy. No therapy has been proven to be effective.

Inpatient Care

With the exception of thyroid storm, Graves disease generally is managed in an outpatient setting.

On occasion, patients may present with thyrotoxic heart disease, including congestive heart failure, atrial fibrillation, or other tachyarrhythmia, which requires inpatient management. Prompt recognition of thyrotoxicosis is required for optimal therapy. In certain cases, the patient may have to be admitted to the intensive care unit or critical care unit. Appropriate subspecialty consultations (eg, endocrinologist, cardiologist) are needed. Once patients' conditions are stabilized, they can be transferred to a regular room or discharged from the hospital.

In certain cases (ie, noncompliant patients, those who develop severe reactions to antithyroid drugs), radioiodine ablation therapy may be given in an inpatient setting.

• References

Surgical Care

Indications and outcomes are as follows:

• Thyroidectomy is not the recommended first-line therapy for hyperthyroid Graves disease in the United States. However, a retrospective cohort study^[73] showed that one-third of all patients electing surgery as definitive management did so without a specific indication, and the patient satisfaction with the decision for surgery as definitive management of Graves disease was high. Surgery is a safe alternative therapeutic option in patients who are noncompliant with or cannot tolerate antithyroid drugs, have moderate-to-severe ophthalmopathy, have large goiters, or refuse or cannot undergo radioiodine therapy. Also, surgical treatment has been found to be more effective than radioiodine therapy to achieve cure and reduce recurrence.^[74]
• Thyroidectomy may be appropriate in the presence of a thyroid nodule that is suggestive of carcinoma.
• In certain cases (eg, in pregnant patients with severe hyperthyroidism), thyroidectomy may be indicated because radioactive iodine and antithyroid medications may be contraindicated.
• It generally is reserved for patients with large goiters with or without compressive symptoms.
• It also may be indicated in patients who refuse radioiodine as definitive therapy or in those in whom the use of antithyroid drugs and/or radioiodine does not control hyperthyroidism.
• Surgery provides rapid treatment of Graves disease and permanent cure of hyperthyroidism in most patients, and it has "negligible mortality and acceptable morbidity" by experienced surgeons.^[75]

Procedures and preparations are as follows:

• Preoperative preparation to render the patient euthyroid is essential in order to prevent thyrotoxic crisis (thyroid storm). The hyperthyroid state can be rapidly corrected using a combination of iopanoic acid, dexamethasone, beta-blockers, and thioamides.^{[76, 77]}
• This can be accomplished with the use of antithyroid drugs for approximately 6 weeks, with or without concomitant beta-blockade.
• Most surgeons administer iodine (as Lugol solution or saturated solution of potassium iodide to provide ≥30 mg of iodine/d) for 10 days before surgery to decrease thyroid gland vascularity, the rate of blood flow, and intraoperative blood loss during thyroidectomy.^{[78, 79, 80]}
• With experienced surgeons, vocal cord paralysis due to superior or recurrent laryngeal nerve injury and hypoparathyroidism are rare adverse events, occurring in less than 1% of patients.
• Subtotal thyroidectomy is usually used with the intention of leaving enough thyroid remnants behind to avoid hypothyroidism.
• Importantly, keep in mind that the risk of recurrent hyperthyroidism potentially increases with larger remnant sizes. However, many studies have shown that the size of the remnant is not the only determinant of the risk of recurrence.
• Iodine uptake and immunologic activity (eg, level of TSI) are just 2 of the other factors that influence the risk of recurrent hyperthyroidism.
• If the goal of surgery is to avoid recurrent hyperthyroidism, near-total thyroidectomy has been advocated as the procedure of choice.
• Regardless of the extent of surgery, all patients require long-term follow-up.

A literature review by Zhang et al comparing endoscopic with conventional open thyroidectomy for Graves disease reported that the endoscopic technique offers better cosmetic satisfaction and less blood loss, while open surgery is associated with reduced operation time. Complication rates for the two techniques with regard to transient recurrent laryngeal nerve palsy, recurrent hyperthyroidism, hypothyroidism, and transient hypocalcemia were equivalent.^[81]

Ophthalmopathy is as follows:

• Near-total thyroidectomy has little, if any, effect on the course of ophthalmopathy.
• If ophthalmopathy is severe but inactive, orbital decompression may be performed. Reducing proptosis and decompressing the optic nerve can be achieved by transantral orbital decompression. A study by Alsuhaibani et al found that the change in the volume of the medial rectus muscle may help explain the variability in the proptosis reduction following orbital decompression.^[82]
• The major adverse effect is postoperative diplopia, which may necessitate a second surgery on the extraocular muscles to correct the problem.
• Rehabilitative (extraocular muscle or eyelid) surgery is often needed. Eyelid surgery (eg, severance of the Müller muscle, scleral or palatal graft insertion) can be performed to improve exposure keratitis.

• References

Consultations

Consultation with an endocrinologist may be necessary for the management and regulation of thyroid hormone levels in atypical presentations, as follows:

• Graves disease in pregnancy
• Neonatal Graves disease management
• Graves disease complicated by a nodular thyroid gland unresponsive to usual medical therapy or in older adults

Consultation with an ophthalmologist may be needed in the following situations:

• Unilateral or bilateral proptosis
• Workup of other etiologies for eye findings besides Graves disease
• Follow-up of visual acuity, corneal disease prevention, and eye muscle function

Consultation with a dermatologist may be needed in patients with localized myxedema that is unresponsive to topical corticosteroids.

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Diet

The amount of iodine in the diet can influence the hormone synthesis activity in the thyroid gland.

Iodine-containing food has different effects on thyroid uptake of¹³¹ I and technetium Tc 99m. Iodine-rich food decreases¹³¹ I uptake but increases^99m Tc in most patients. However, the diagnostic value of a radioiodine uptake test to differentiate Graves disease and silent thyroiditis is not affected by dietary iodine intake.^[83] Iodine restriction before a radioiodine uptake test is unnecessary.

Dietary iodine intake may influence the remission rate after antithyroid drug therapy. This is based on the observation that the outcome of antithyroid therapy in the older literature showed lower remission rates than it did in later studies and that the average dietary iodine content has been decreasing over the years. However, a direct causal relationship has not been established by clinical trials.

In addition, the use of antithyroid drug therapy for more than 2 years is a good predictor of Graves disease.^[84] In pediatric patients with Graves disease, no difference was noted in remission rates between methimazole and PTU, while minor adverse effects were significantly increased in patients receiving PTU doses of 7.5 mg/kg or higher.^[85]

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Activity

Given the high-output state of the heart, strenuous exercise may be detrimental. The patient should be advised to avoid severe fatigue from exercise. Patients can use their pulse as a guide to activity.

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Complications

Agranulocytosis is an idiosyncratic reaction to antithyroid drugs. The role of serial CBC counts to predict who will develop this serious adverse reaction is not well established.

In contrast to patients with Graves disease, preoperative iodine treatment should not be given to patients with toxic nodular goiters because it can exacerbate hyperthyroidism.

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Prevention

Prevention is difficult because of the lack of knowledge regarding the pathogenesis of this condition.

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Long-Term Monitoring

Hyperthyroidism represents a continuum of thyroid dysfunction. In the case of thyroid storm, decompensated patients with hyperthyroidism should be cared for in an institution with personnel familiar with this disease.

All patients should receive long-term follow-up, regardless of the mode of therapy (ie, surgery, radioiodine, antithyroid drugs).

Close follow-up visits with monitoring of examination findings, thyroid hormone levels, and thyrotropin levels are required.

If the patient is on antithyroidal medication (eg, thioamides), liver function tests and CBC counts with differentials should be monitored based on the clinical situation.

Examination of the eyes should be a routine part of follow-up of these patients, given the lack of predictability of ophthalmopathy.

Smoking cessation techniques should be continued.

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Guidelines Summary

In 2016, the American Thyroid Association updated the 2011 hyperthyroidism/thyrotoxicosis guidelines it had codeveloped with the American Association of Clinical Endocrinologists. The following are a sampling of the 124 evidence-based recommendations included in the guideline update^[86] :

• Beta-adrenergic blockade is recommended in all patients with symptomatic thyrotoxicosis, especially elderly patients and thyrotoxic patients with resting heart rates in excess of 90 beats per minute or coexistent cardiovascular disease
• Patients with overt Graves hyperthyroidism should be treated with any of the following modalities: radioactive iodine therapy, antithyroid drugs, or thyroidectomy
• If methimazole is chosen as the primary therapy for Graves disease, the medication should be continued for approximately 12-18 months and then discontinued if the serum thyrotropin and thyrotropin receptor antibody levels are normal at that time
• If surgery is chosen as the primary therapy for Graves disease, near-total or total thyroidectomy is the procedure of choice
• If surgery is chosen as treatment for toxic multinodular goiter, near-total or total thyroidectomy should be performed
• If surgery is chosen as the treatment for toxic adenoma, a thyroid sonogram should be done to evaluate the entire thyroid gland; an ipsilateral thyroid lobectomy (or isthmusectomy, if the adenoma is in the thyroid isthmus), should be performed for isolated toxic adenomas
• Children with Graves disease should be treated with methimazole, radioactive iodine therapy, or thyroidectomy; radioactive iodine therapy should be avoided in very young children (< 5 years); radioactive iodine therapy in children is acceptable if the activity is over 150 μCi/g (5.55 MBq/g) of thyroid tissue and for children between ages 5 and 10 years if the calculated radioactive iodine administered activity is under 10 mCi (< 473 MBq); thyroidectomy should be chosen when definitive therapy is required, the child is too young for radioactive iodine, and surgery can be performed by a high-volume thyroid surgeon
• If methimazole is chosen as the first-line treatment for Graves disease in children, it may be tapered in those children requiring low doses after 1-2 years to determine if a spontaneous remission has occurred, or it may be continued until the child and caretakers are ready to consider definitive therapy, if needed
• If surgery is chosen as therapy for Graves disease in children, total or near-total thyroidectomy should be performed
• Euthyroidism should be expeditiously achieved and maintained in hyperthyroid patients with Graves ophthalmopathy or risk factors for the development of ophthalmopathy
• In patients with Graves hyperthyroidism who have mild active ophthalmopathy and no risk factors for deterioration of their eye disease, radioactive iodine therapy, antithyroid drugs, and thyroidectomy should be considered equally acceptable therapeutic options
• In Graves disease patients with mild Graves ophthalmopathy who are treated with radioactive iodine, steroid coverage is recommended if there are concomitant risk factors for Graves ophthalmopathy deterioration

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Medication Summary

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

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Propylthiouracil

• Dosing, Interactions, etc.

Clinical Context:  Derivative of thiourea that inhibits organification of iodine by thyroid gland. Blocks oxidation of iodine in thyroid gland, thereby inhibiting thyroid hormone synthesis; inhibits T4-to-T3 conversion by blocking type I deiodinase (advantage over other agents). Usual course/duration of therapy is 1-2 y; sustained remission more likely after 1-2 y vs 3-6 mo of therapy.

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Methimazole (Tapazole)

• Dosing, Interactions, etc.

Clinical Context:  Inhibits thyroid hormone by blocking oxidation of iodine in thyroid gland; however, not known to inhibit peripheral conversion of thyroid hormone. Considerable debate surrounds optimal dosage/duration.

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Class Summary

Thioamides function as antithyroid agents mainly by inhibiting iodide organification and coupling processes, thereby preventing synthesis of thyroid hormones. Half-life of T4 is 7 d in persons who are euthyroid and somewhat shorter in patients who are thyrotoxic. This accounts for a several-week delay in onset of clinical improvement in most patients. Agents have been reported to alter intrathyroidal immunoregulatory mechanisms. Only oral preparations are available, but they have been used as retention enemas in patients in whom oral intake is not possible or is contraindicated.

Although these agents fall under pregnancy category D, they have been used safely in many pregnant patients. Retrospective study indicates rate of major congenital malformations with PTU (3%) or methimazole (2.7%) was not significantly different from normal background rate (2-5%). Duration of treatment ranged from 0-23 wk, with doses ranging from 100-600 mg/d of PTU or 10-60 mg/d of methimazole.

Concentrations of methimazole are higher in breast milk; therefore, PTU is preferred in this patient population.

Risk of agranulocytosis is similar (0.2-0.5%) in members of this class. In general, PTU is associated with transaminase elevation in susceptible individuals, while methimazole may cause a cholestatic effect.^[87]

The US Food and Drug Administration (FDA) added a boxed warning, the strongest warning issued by the FDA, to the prescribing information for PTU. The boxed warning emphasizes the risk for severe liver injury and acute liver failure, some of which have been fatal. The boxed warning also states that PTU should be reserved for use in patients who cannot tolerate other treatments, such as methimazole, radioactive iodine, or surgery.

Medically treated Graves disease has a significant risk of relapse (23% within 6 months of discontinuation of antithyroid medication and 42% within 5 years). The presence of goiter is associated with an increased risk of relapse after medical therapy.^[88]

The decision to include a boxed warning was based on the FDA's review of postmarketing safety reports and on meetings held with the American Thyroid Association, the National Institute of Child Health and Human Development, and the pediatric endocrine clinical community.

The FDA has identified 32 cases (22 adult and 10 pediatric) of serious liver injury associated with PTU. Of the adults, 12 deaths and 5 liver transplants occurred, and among the pediatric patients, 1 death and 6 liver transplants occurred. PTU is indicated for hyperthyroidism due to Graves disease. These reports suggest an increased risk for liver toxicity with PTU compared with methimazole. Serious liver injury has been identified with methimazole in 5 cases (3 resulting in death).

PTU is considered to be a second-line drug therapy, except in patients who are allergic to or intolerant of methimazole, or in women who are in the first trimester of pregnancy. Rare cases of embryopathy, including aplasia cutis, have been reported with methimazole during pregnancy. The FDA recommends the following criteria be considered for prescribing PTU (for more information, see the FDA Safety Alert):

- Reserve PTU use during first trimester of pregnancy, or in patients who are allergic to or intolerant of methimazole.

- Closely monitor PTU therapy for signs and symptoms of liver injury, especially during the first 6 months after initiation of therapy.

- For suspected liver injury, promptly discontinue PTU therapy, evaluate the patient for evidence of liver injury, and provide supportive care.

- PTU should not be used in pediatric patients unless the patient is allergic to or intolerant of methimazole and no other treatment options are available.

- Counsel patients to promptly contact their health care provider for the following signs or symptoms: fatigue, weakness, vague abdominal pain, loss of appetite, itching, easy bruising, or yellowing of the eyes or skin.

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Propranolol (Inderal, Inderal LA)

• Dosing, Interactions, etc.

Clinical Context:  DOC in treating cardiac arrhythmias resulting from hyperthyroidism. Controls cardiac and psychomotor manifestations within minutes.

Drug completely absorbed from GI tract; because of extensive first-pass metabolism in liver, systemic bioavailability affected by hepatic blood flow, intrinsic clearance in liver, and genetic and age differences in individuals.

Dosage prediction for IV from prior PO difficult; therefore, careful titration of IV dose necessary.

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Atenolol (Tenormin)

• Dosing, Interactions, etc.

Clinical Context:  Selectively blocks beta1 receptors with little or no effect on beta2 types. Useful in treating cardiac arrhythmias resulting from hyperthyroidism.

• References

Class Summary

Both cardioselective and noncardioselective types are important adjuncts in treating hyperthyroidism. Beta-blockade provides rapid relief of hyperadrenergic symptoms and signs of thyrotoxicosis (eg, palpitations, tremors, anxiety, heat intolerance, various eyelid signs) before any decrease in thyroid hormone levels demonstrated. Also useful in preventing episodes of hypokalemic periodic paralysis in susceptible individuals. DOC for thyroiditis, which is self-limiting. High-dose propranolol can inhibit peripheral T4-to-T3 conversion. Also useful in preparing thyrotoxic patients for surgery.

• References

Potassium iodide (SSKI, Pima)

• Dosing, Interactions, etc.

Clinical Context:  Inhibits thyroid hormone secretion.

Contains 5% iodine and 10% potassium iodide. Contains 8 mg of iodide per drop. May be mixed with juice or water for intake.

• References

Diatrizoate (Hypaque sodium)

• Dosing, Interactions, etc.

Clinical Context:  Blocks release of thyroid hormones.

• References

Iopanoic acid (Telepaque)

Clinical Context:  Oral contrast agent for rapid and significant inhibition of peripheral T4-to-T3 conversion. Inorganic iodide released also blocks release of thyroid hormones.

• References

Class Summary

Have long been used to treat thyrotoxicosis and are still important adjunctive therapy for hyperthyroidism in modern medicine. In pharmacologic concentrations (100-times normal plasma level), decrease activity of thyroid gland. Action involves decreasing thyroidal iodide uptake, decreasing iodide oxidation and organification, and blocking release of thyroid hormones (Wolff-Chaikoff effect).

Oral contrast agents ipodate or iopanoic acid also shown to be potent inhibitors of T4-to-T3 conversion, making them ideal for severe or decompensated thyrotoxicosis. Generally administered after thioamide is started. Also used as preoperative preparation for thyroid surgery for Graves disease.

In combination with thioamides and/or propranolol, iodines are used routinely before thyroidectomy. Iodines are given for 2-3 weeks before surgery and decrease vascularity of hyperthyroid gland. Making patient euthyroid before surgery prevents intraoperative and postoperative complications.

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Cholestyramine (Questran)

• Dosing, Interactions, etc.

Clinical Context:  Can be used to lower serum thyroid hormone levels. This cholesterol-lowering resin has been used as adjunctive therapy in management of hyperthyroid Graves disease. Proved to be effective and well-tolerated adjunctive therapy, leading to a more rapid reduction of thyroid hormone levels.

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Class Summary

Based on the observation that a small portion of L-thyroxine is usually reabsorbed in the bowel and recycled in the enterohepatic circulation, exchange resins have been used to bind thyroid hormones in the GI tract. Enterohepatic circulation of thyroxine is increased in cases of hyperthyroidism.

• References

Lithium (Lithotabs, Eskalith, Lithobid)

• Dosing, Interactions, etc.

Clinical Context:  Patients intolerant to iodine can be treated with lithium, which also impairs thyroid hormone release. Can be used in patients who cannot take PTU or MMI. Use of iodine alone is debatable.

• References

Class Summary

Act in a manner similar to iodine but is not routinely used because of transient effect and risk of potentially serious adverse effects. Now primarily used as a backup agent when other first-line agents are contraindicated because of hypersensitivity or toxicity.

• References

Amiodarone (Cordarone)

• Dosing, Interactions, etc.

Clinical Context:  Case report described successful normalization of thyroid hormone level in a patient with Graves disease who had fulminant PTU-induced hepatitis. However, experience and information in treatment of Graves disease is scant.

• References

Class Summary

Amiodarone, an iodinated benzofuran, is an important antiarrhythmic medication that also alters thyroid hormone metabolism. High iodine content of this molecule (37.5%) is responsible for hypothyroidism. On the other hand, amiodarone can lead to hyperthyroidism through 2 complex mechanisms. Type I amiodarone-induced thyrotoxicosis is due to increased thyroid hormone synthesis and release in patients with multinodular goiter or Graves disease, while type II amiodarone-induced thyrotoxicosis is a destructive thyroiditis with release of preformed thyroid hormone.

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Prednisone (Sterapred)

• Dosing, Interactions, etc.

Clinical Context:  Has been customarily used in management of Graves ophthalmopathy. Other oral glucocorticoids at equipotent doses may also be effective.

• References

Methylprednisolone (Solu-Medrol)

• Dosing, Interactions, etc.

Clinical Context:  Has been customarily used for high-dose pulse steroid therapy in management of Graves ophthalmopathy. Other glucocorticoids at equipotent doses may also be effective. Intravenous high dose glucocorticoid therapy may be more effective and better tolerated than oral steroid therapy in the management of Graves ophthalmopathy (Aktaran, 2007).

• References

Dexamethasone (Decadron)

• Dosing, Interactions, etc.

Clinical Context:  In healthy persons, induces decrease in serum T3 levels without a change in serum T4 levels, suggesting an effect of dexamethasone on peripheral T3-to-T4 conversion.

In patients with Graves hyperthyroidism, induces rapid fall in serum thyroid hormone levels. Changes are too rapid to be explained by a steroid-induced fall in the level of a circulating IgG thyroid stimulator (TSI). Mechanism for this observation is unclear.

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Class Summary

Graves disease is an autoimmune disease. Although glucocorticoids have been shown to decrease T4-to-T3 conversion and decrease thyroid hormones by yet undiscovered mechanisms, the adverse effect profile of long-term glucocorticoid therapy makes it unattractive for long-term management of Graves hyperthyroidism. However, glucocorticoids may have a role in rapidly lowering thyroid hormone levels in the clinical setting of thyroid storm. With regard to Graves ophthalmopathy, current evidence indicates that glucocorticoids represent the only class of drug therapy that, either alone or combined with other therapies, has an unequivocal role in management.

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Metoprolol (Lopressor, Toprol XL)

• Dosing, Interactions, etc.

Clinical Context:  Selective beta1-adrenergic receptor blocker that decreases automaticity of contractions. Useful in treating cardiac arrhythmias resulting from hyperthyroidism. During IV administration, carefully monitor BP, heart rate, and ECG.

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