In 1656, Thomas Wharton described the distinct nature of what he termed the thyroid gland, distinguishing it from the larynx, as this structure had been considered a laryngeal gland from the time of Andreas Vesalius in the 16th century. It was nearly 200 more years before the function of the thyroid was elucidated. The normal adult thyroid gland weighs 10-25 g and has 2 lobes connected by an isthmus. Nearly 50% of thyroid glands exhibit a pyramidal lobe arising from the center of the isthmus. Longitudinal dimensions of the lobes of the thyroid range up to 5 cm, as shown in the image below.
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Thyroid nuclear scan of a patient with a euthyroid goiter showing different projections.
A goiter is an enlarged thyroid gland, and it may be diffuse or nodular. A goiter may extend into the retrosternal space, with or without substantial anterior enlargement. Because of the anatomic relationship of the thyroid gland to the trachea, larynx, superior and inferior laryngeal nerves, and esophagus, abnormal growth may cause a variety of compressive syndromes. Thyroid function may be normal (nontoxic goiter),[1] overactive (toxic goiter), or underactive (hypothyroid goiter).
The thyroid gland is controlled by thyroid-stimulating hormone (TSH; also known as thyrotropin), secreted from the pituitary gland, which in turn is influenced by the thyrotropin-releasing hormone (TRH) from the hypothalamus. TSH permits growth, cellular differentiation, and thyroid hormone production and secretion by the thyroid gland. Thyrotropin acts on TSH receptors located on the thyroid gland. Thyroid hormones are synthesized from iodination of tyrosine. The iodine is transported from plasma into the thyroid cell via a sodium-iodide symporter. This is an active process resulting in an intracellular iodine level exceeding 20 times the plasma iodine level. This iodine transport activity is controlled by TSH.[2] Serum thyroid hormones levothyroxine and triiodothyronine feed back to the pituitary, regulating TSH production. Interference with this TRH-TSH thyroid hormone axis causes changes in the function and structure of the thyroid gland. Stimulation of the TSH receptors of the thyroid by TSH, TSH-receptor antibodies, or TSH receptor agonists, such as chorionic gonadotropin, may result in a diffuse goiter. When a small group of thyroid cells, inflammatory cells, or malignant cells metastatic to the thyroid is involved, a thyroid nodule may develop.
A deficiency in thyroid hormone synthesis or intake leads to increased TSH production. Increased TSH causes increased cellularity and hyperplasia of the thyroid gland in an attempt to normalize thyroid hormone levels. If this process is sustained, a goiter is established. Causes of thyroid hormone deficiency include inborn errors of thyroid hormone synthesis, iodine deficiency,[3] and goitrogens.
A goiter may result from a number of TSH receptor agonists. TSH receptor stimulators include TSH receptor antibodies, pituitary resistance to thyroid hormone, adenomas of the hypothalamus or pituitary gland, and tumors producing human chorionic gonadotropin.
Autopsy studies suggest a frequency of greater than 50% for thyroid nodules; with high-resolution ultrasonography, the value approaches 40% of patients with nonthyroidal illness. In the Framingham study, ultrasonography revealed that 3% of men older than 60 years had thyroid nodules, while 36% of women aged 49-58 years had thyroid nodules.[4] In the United States, most goiters are due to autoimmune thyroiditis (ie, Hashimoto disease).
International
Worldwide, the most common cause of goiter is iodine deficiency.[3] It is estimated that goiters affect as many as 200 million of the 800 million people who have a diet deficient in iodine. In the Wickham study from the United Kingdom, 16% of the population had a goiter.[5]
In a German study, 635 people underwent ultrasonographic thyroid screening, as well as basal TSH measurement, during a preventive-health checkup.[6] Thyroid nodules were detected in 432 (68%) of the persons screened; in a previous German study, ultrasonographic screening of more than 90,000 people detected thyroid nodules in 33% of the normal population. The authors of the latter report attributed this difference to the fact that patients in their study were screened using 13 MHz ultrasonographic scanners, which were more sensitive than the 7.5 MHz scanners used in the previous study. According to the investigators, their results indicated that the question of routine iodine supplementation requires renewed attention.
The incidence of thyroid cancer has been rising worldwide. The reasons are unclear, but this trend may be related to better detection and diagnostic methods.[7]
Mortality/Morbidity
Most goiters are benign, causing only cosmetic disfigurement. Morbidity or mortality may result from compression of surrounding structures, thyroid cancer, hyperthyroidism, or hypothyroidism.
Race
No racial predilection exists.
Sex
The female-to-male ratio is 4:1.
In the Wickham study, 26% of women had a goiter, compared to 7% of men.[5]
Thyroid nodules are less frequent in men than in women, but when found, they are more likely to be malignant.
Age
The frequency of goiters decreases with advancing age. The decrease in frequency differs from the incidence of thyroid nodules, which increases with advancing age.
Benign goiters have a good prognosis. However, all goiters should be monitored by examination and biopsy for possible malignant transformation, which may be signaled by a sudden change in size, pain, or consistency. Fortunately, the risk of this is low. In patients exposed to low levels of radiation the risk rises.
Based on the Wickham study, a few of the goiters increased in size.[5]
A small percentage of multinodular goiters do cause hyperthyroidism. Lifelong surveillance is necessary.
Patients with chronic lymphocytic thyroiditis generally have glands that become atrophic.
A study by Sorensen et al found that patients with symptomatic benign nodular goiter who underwent thyroidectomy experienced improvements in tracheal anatomy, inspiratory flow, and health-related quality of life. The investigators found a median 26% improvement in tracheal narrowing and 33% diminishment in tracheal deviation, at 6 months postsurgery. The study also reported a 1% improvement in tracheal narrowing for each 10% reduction in goiter volume. In addition, forced inspiratory flow at 50% of forced vital capacity showed a small improvement. With regard to quality of life, the Impaired Daily Life scale from the Thyroid-Specific Patient-Reported Outcome Measure (ThyPRO) improved by 0.33-points for every 1% reduction in tracheal narrowing.[8, 9]
Educate a patient about potential etiologies, eg, adequate dietary iodine intake, avoidance of goitrogens, regular personal neck examination, and physician examination.
For patients on medical therapy, reinforce the need to take medications on a regular basis. Review symptoms of hyperthyroidism.
For excellent patient education resources, visit eMedicineHealth's Thyroid and Metabolism Center. Also, see eMedicineHealth's patient education article Thyroid Problems.
The general examination for hyperthyroidism, hypothyroidism, and autoimmune stigmata is followed by systematic examination of the goiter.
A retrosternal goiter may not be evident on physical examination.
Examination of the goiter is best performed with the patient upright, sitting or standing. Inspection from the side may better outline the thyroid profile, as shown below. Asking the patient to take a sip of water facilitates inspection. The thyroid should move upon swallowing. See the image below.
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Patient with a goiter. Prominent side-view outline.
Palpation of the goiter is performed either facing the patient or from behind the patient, with the neck relaxed and not hyperextended. Palpation of the goiter rules out a pseudogoiter, which is a prominent thyroid seen in individuals who are thin. Each lobe is palpated for size, consistency, nodules, and tenderness. Cervical lymph nodes are then palpated. The oropharynx is visualized for the presence of lingular thyroid tissue.
The size of each lobe is measured in 2 dimensions using a tape measure. Some examiners make tracings on a sheet of paper, which is placed in the patient's chart. Suitable landmarks are used and documented to ensure consistent measurement of the thyroid gland.
The pyramidal lobe often is enlarged in Graves disease.
A firm rubbery thyroid gland suggests Hashimoto thyroiditis, and a hard thyroid gland suggests malignancy or Riedel struma.
Multiple nodules may suggest a multinodular goiter or Hashimoto thyroiditis. A solitary hard nodule suggests malignancy, whereas a solitary firm nodule may be a thyroid cyst.
Diffuse thyroid tenderness suggests subacute thyroiditis, and local thyroid tenderness suggests intranodal hemorrhage or necrosis.
Cervical lymph glands are palpated for signs of metastatic thyroid cancer.
Auscultation of a soft bruit over the inferior thyroidal artery may be appreciated in a toxic goiter. Palpation of a toxic goiter may reveal a thrill in the profoundly hyperthyroid patient.
Goiters are described in a variety of ways, including the following:
Toxic goiter: A goiter that is associated with hyperthyroidism is described as a toxic goiter. Examples of toxic goiters include diffuse toxic goiter (Graves disease), toxic multinodular goiter, and toxic adenoma (Plummer disease).
Nontoxic goiter: A goiter without hyperthyroidism or hypothyroidism is described as a nontoxic goiter. It may be diffuse or multinodular, but a diffuse goiter often evolves into a nodular goiter. Examination of the thyroid may not reveal small or posterior nodules. Examples of nontoxic goiters include chronic lymphocytic thyroiditis (Hashimoto disease), goiter identified in early Graves disease, endemic goiter, sporadic goiter, congenital goiter, and physiologic goiter that occurs during puberty.
Autonomously functioning nodules may present with inability to palpate the contralateral lobe. Unilobar agenesis may also present like a single thyroid nodule with hyperplasia of the remaining lobe.
The Pemberton maneuver raises a goiter into the thoracic inlet when the patient elevates the arms. This may cause shortness of breath, stridor, or distention of neck veins.
Initial screening should include TSH. Given the sensitive third-generation assays in the absence of symptoms of hyper or hypothyroidism further testing is not required. An assessment of free thyroxine index or direct measurement of free thyroxine would be the next step in the evaluation.
Further laboratory testing is based on presentation and results of screening studies and may include thyroid antibodies (antithyroid peroxidase formerly the antimicrosomal antibodies and antithyroglobulin), thyroglobulin, sedimentation rate and calcitonin in an individual at high risk for medullary carcinoma of the thyroid.
Ultrasonography can be used to establish and follow goiter size, consistency, and nodularity.[6] It can also be employed to localize nodules for ultrasonographically guided biopsy.
A study by Kelly et al indicated that in some patients with multinodular goiter, the risk of neoplasia can be effectively assessed with ultrasonography rather than with fine-needle aspiration biopsy. The investigators reported that in study patients with no suspicious features on ultrasonography, the average risk of neoplasia in multinodular goiters was 0.0339, although this risk rose significantly when one or more suspicious features were present.[12]
Roentgenography
Roentgenography is used to assess extent of a goiter and presence of calcification. Ultrasonography has replaced this modality.
Roentgenography is used to visualize calcifications within a goiter and regional lymph glands.
Computed tomography (CT) scanning
CT scanning is more precise than roentgenography.
CT scanning can be used to delineate size and goiter extent. Due to the superficial placement of the thyroid gland, ultrasonography is more useful in following size. CT scanning does a much better job of determining the effect of the thyroid gland on nearby structures. It also may be useful in the follow-up of patients with thyroid cancer that shows evidence of recurrence.
CT scanning can be used to guide biopsy of the thyroid.
MRI
Magnetic resonance imaging has the same indications as CT scanning (see above).
Radionuclide uptake and radionuclide scanning are used to assess thyroid function and anatomy in hyperthyroidism, as shown below. Additionally, thyroid scanning may be useful in the patient with neck or superior mediastinal masses. Radionuclide scanning allows determination of the function of a nodule. Function of a thyroid nodule has value both diagnostically and therapeutically. See the image below.
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Thyroid nuclear scan of a patient with a euthyroid goiter showing different projections.
Other
Barium swallow is used to assess esophageal obstruction.
Spirometry: The flow-volume loop is useful in determining the functional significance of compressive goiters.
Perchlorate discharge test is used in individuals with inborn errors of thyroid hormone synthesis. It is used rarely today to determine the ability to trap and organify iodine.
Fine-needle aspiration biopsy is used for cytologic diagnosis.[13] Fine-needle aspiration of the thyroid is used to determine the cause of an enlarged gland. In general, the procedure is not used in the workup of autonomously functioning nodules. The procedure has little morbidity and can be tailored to the situation.
Core biopsy, or large-needle biopsy, of the thyroid uses a larger gauge needle providing a fragment of tissue. This procedure also carries with it a higher morbidity. Core biopsy has the advantage of more complete sampling.
Partial thyroidectomy may be used as a first-line procedure for patients with a high probability of cancer. It is reserved mostly if the result of a fine-needle aspiration is suspicious or if the patient/physician prefers it.
Total thyroidectomy is performed for malignant goiters.
Simple nontoxic goiters show hyperplasia, colloid accumulation, and nodularity. Nodular hyperplasia is commonly seen in multinodular goiter. Cytologic findings include benign appearing follicular cells, abundant colloid, macrophages, and, sometimes, Hürthle cells. Inflammatory disorders of the thyroid, such as chronic lymphocytic (Hashimoto) thyroiditis, contain a mixed population of lymphocytes mixed with benign appearing follicular cells. Malignant nodules may be follicular cell in origin, ie, papillary (most common), follicular, Hürthle cell, or anaplastic. They also may be from parafollicular cells, medullary carcinoma or lymphoma, or other categories.
Small benign euthyroid goiters do not require treatment. The effectiveness of medical treatment using thyroid hormone for benign goiters is controversial. Large and complicated goiters may require medical and surgical treatment. Malignant goiters require medical and surgical treatment.
The size of a benign euthyroid goiter may be reduced with levothyroxine suppressive therapy. The patient is monitored to keep serum TSH in a low but detectable range to avoid hyperthyroidism, cardiac arrhythmias, and osteoporosis. The patient has to be compliant with monitoring. Some authorities suggest suppressive treatment for a definite time period instead of indefinite therapy. Patients with Hashimoto thyroiditis respond better.
Treatment of hypothyroidism or hyperthyroidism often reduces the size of a goiter.
Thyroid hormone replacement is often required following surgical and radiation treatment of a goiter. Use of radioactive iodine for the therapy of nontoxic goiter has been disappointing and is controversial.
Medical therapy of autonomous nodules with thyroid hormone is not indicated.
Ethanol infusion into benign thyroid nodules has not been approved in the United States, but it is used elsewhere.
Goiters with primary thyroid malignancy require levothyroxine replacement after surgery and radioactive iodine ablation. Metastatic lesions to the thyroid gland require treatment of the primary malignancy. Granulomatous and infectious etiologies for goiter require specific treatment depending on the underlying cause.
When other forms of therapy are not practical or ineffective
Preoperatively, establish euthyroid state prior to surgical treatment. Evaluation must include the stability of the airway. This must be secured immediately if ventilatory status appears tenuous. Emergency surgical treatment of a goiter in a patient with hypothyroidism requires intravenous levothyroxine and glucocorticoids at stress doses.
Emergency surgical treatment of a goiter in a thyrotoxic patient requires antithyroid medications, beta blockers, and glucocorticoids at stress doses. Suppressive doses of iodine are helpful.
Intraoperative and postoperative management includes hemodynamic monitoring, which is important in patients with preoperative hyperthyroidism or hypothyroidism.
Postoperative management also includes monitoring of serum calcium.
A literature review by Li et al indicated that total thyroidectomy is a safe procedure for the treatment of bilateral multinodular nontoxic goiter, demonstrating a lower recurrence rate than bilateral subtotal thyroidectomy. However, total thyroidectomy was also found to carry a significantly higher risk of postoperative transient hypoparathyroidism than did the other procedure.[14]
A study by Khan et al indicated that in patients with retrosternal goiter, a transcervical surgical approach is preferable to a transthoracic procedure. The study, which employed the National Surgical Quality Improvement Program (NSQIP) database, found that various postoperative morbidities, including those involving transfusions and unplanned intubations, were higher with the transthoracic approach. The data suggested that overall mortality might be increased as well with this procedure.[15]
A study by Bove et al indicated that in patients with retrosternal goiter, recurrence and extension of the goiter beyond the carina are preoperative risk factors for postoperative complications following total thyroidectomy. The study also found evidence that compared with total thyroidectomy for cervical goiter, the risk for transient hypocalcemia and transient recurrent laryngeal nerve palsy is greater following the same procedure for retrosternal goiter.[16]
An endocrinologist should assess a patient at least once, and assessment should be even more frequent if the goiter is complicated by thyroid dysfunction or malignancy or if the patient is being considered for surgical management.
Nutrition plays a role in the development of endemic goiters. Dietary factors include iodine deficiency, goitrogens, protein malnutrition, and energy malnutrition. Often these factors occur concurrently.
Iodine: If it is practical, treat endemic goiters in iodine-deficient regions with iodine supplementation in the diet and avoidance of goitrogens. Treatment with iodine supplementation or levothyroxine may reduce goiter size.[3]
Goitrogens: Cyanoglucosides are naturally occurring goitrogens that are digested to release cyanide, which is converted to thiocyanate. Thiocyanate inhibits iodide transport in the thyroid and, at higher levels, inhibits organification. Foods that contain cyanoglucosides include cassava, lima beans, maize, bamboo shoots, and sweet potatoes. Thioglucosides are natural goitrogens found in the Cruciferae family of vegetables and weeds eaten by animals. When digested, they release thiocyanate and isothiocyanate, which have thionamidelike properties and are passed to humans via milk ingestion.
Correct iodine deficiency[3] and avoid dietary or iatrogenic goitrogens if practical. In the United States, it is difficult to find iodine deficiency, given the supplementation of table salt with iodine, iodine in cattle feed, and the use of iodine as a dough conditioner. Judicious use of levothyroxine is helpful in patients with a previous diagnosis of nodular hyperplasia who have had a lobectomy to prevent occurrences in the contralateral lobe.
Goiters due to autoimmune thyroiditis may be controlled with careful use of levothyroxine and, when indicated, anti-inflammatory medication.
Congenital goiters due to inborn errors of metabolism may be reduced or prevented by careful use of levothyroxine during the postpartum period. Newborns are screened for congenital hypothyroidism.
Clinical Context:
Synthetic thyroxine is converted to the active form, triiodothyronine by 5'-deiodinase. Within the pituitary, type-II deiodinase helps convert T4 to T3, which in turn regulates TSH production, the main growth factor for the thyroid gland.
Benign goiters can be treated with thyroid hormone. The most widely used thyroid hormone is levothyroxine sodium, administered once a day. Liothyronine sodium requires more frequent administration. Desiccated thyroid powder, thyroglobulin, and liotrix are less predictable following ingestion.
What is a goiter?What is the pathophysiology of goiter?What is the prevalence of goiter in the US?What is the global prevalence of goiter?What causes mortality and morbidity in patients with goiter?What is the racial predilection for goiter?How does the incidence of goiter vary by sex?Which age group has the highest prevalence of goiter?What is the prognosis of goiter?What should be included in patient education about goiter?What are the signs and symptoms of goiter?How is the physical exam for goiter performed?How is palpation of the goiter performed?What is the difference between a toxic and nontoxic goiter?What is the role of Pemberton maneuver in the evaluation of the goiter?What causes a goiter?What are the differential diagnoses for Goiter?Which lab studies are performed in the diagnosis for goiter?What is the role of ultrasonography in the diagnosis for goiter?What is the role of roentgenography in the diagnosis for goiter?What is the role of CT scanning and MRI in the diagnosis for goiter?What is the role of radionuclide scanning in the diagnosis for goiter?What is the role of pulmonary function testing in the diagnosis for goiter?What is the role of a perchlorate discharge test in the diagnosis for goiter?What is the role of biopsy in the diagnosis for goiter?What is the role of thyroidectomy in the management of goiter?Which histologic findings are characteristic of goiter?What are the medical treatment options for goiter?What is the role of surgery in the treatment of goiter?How is surgery performed in the treatment of goiter?Which specialist consultations are beneficial for patients with goiter?What is the role of dietary modifications in the treatment of goiter?What are the potential complications of goiter?How is goiter prevented?How are patients with goiter monitored?What is the goal of drug treatment for goiter?Which medications in the drug class Thyroid hormone replacements are used in the treatment of Goiter?
James R Mulinda, MD, FACP, Consulting Staff, Department of Endocrinology, Endocrinology Associates, Inc
Disclosure: Nothing to disclose.
Specialty Editors
Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Received salary from Medscape for employment. for: Medscape.
Kent Wehmeier, MD, Professor, Department of Internal Medicine, Division of Endocrinology, Diabetes, and Metabolism, St Louis University School of Medicine
Disclosure: Nothing to disclose.
Chief Editor
Romesh Khardori, MD, PhD, FACP, Professor of Endocrinology, Director of Training Program, Division of Endocrinology, Diabetes and Metabolism, Strelitz Diabetes and Endocrine Disorders Institute, Department of Internal Medicine, Eastern Virginia Medical School
Disclosure: Nothing to disclose.
Additional Contributors
Steven R Gambert, MD, Professor of Medicine, Johns Hopkins University School of Medicine; Director of Geriatric Medicine, University of Maryland Medical Center and R Adams Cowley Shock Trauma Center
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