Updated: Aug 18, 2009
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. (See image below and Image 1.)
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. 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,1 and goitrogens.
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 Wickham study from the United Kingdom, 16% of the population had a goiter.2 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.3 In the United States, most goiters are due to autoimmune thyroiditis (ie, Hashimoto disease).
Worldwide, the most common cause of goiter is iodine deficiency.1 It is estimated that goiters affect as many as 200 million of the 800 million people who have a diet deficient in iodine.
In a German study, 635 people underwent ultrasonographic thyroid screening, as well as basal TSH measurement, during a preventive-health checkup.4 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 later 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.
Most goiters are benign, causing only cosmetic disfigurement. Morbidity or mortality may result from compression of surrounding structures, thyroid cancer, hyperthyroidism, or hypothyroidism.
No racial predilection exists.
The female-to-male ratio is 4:1.
The frequency of goiters decreases with advancing age. The decrease in frequency differs from the incidence of thyroid nodules, which increases with advancing age.
A goiter may present in various ways, including the following:
The general examination for hyperthyroidism, hypothyroidism, and autoimmune stigmata is followed by systematic examination of the goiter.
The different etiologic mechanisms that can cause a goiter include the following:
| Lipomas | Thyroid, Papillary Carcinoma |
| Thyroid Lymphoma | Thyroiditis, Subacute |
| Thyroid Nodule | |
| Thyroid, Anaplastic Carcinoma | |
| Thyroid, Medullary Carcinoma |
Branchial cleft cyst
Thyroglossal duct cyst
Cystic hygroma
Pseudogoiter
Lymphadenopathy
Carotid artery aneurysm
Parathyroid cyst
Parathyroid adenoma
Sarcoma
Fibroma
Thyroid abscess
Granulomatous disease of the thyroid
Infectious thyroiditis
Thyrotoxicosis
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.
Surgery is reserved for the following situations:
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.
The goals of pharmacotherapy are to reduce morbidity and to prevent complications.
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.
Synthetic thyroxine is converted to the active form, triiodothyronine, in the pituitary by 5'-deiodinase. Inhibits production of thyrotropin, which is the main growth factor for the thyroid gland.
1.5-2.5 mcg/kg PO qd; use lowest dose possible for TSH suppression; over-replacement of thyroid hormone is to be avoided in older patients; lower doses, more frequent monitoring, and slower titration are necessary in these individuals
5-10 mcg/kg PO qd; younger patients require higher dose for TSH suppression
Increases metabolism of most drugs and may compete for protein transport sites; absorption reduced by iron, bile sequestrants, and antacids; cholestyramine may decrease liothyronine absorption; estrogen may decrease response to thyroid hormone therapy in patients with nonfunctioning thyroid glands; effect of anticoagulants increases when administered with liothyronine; activity of some beta-blockers may decrease when patient with hypothyroidism is converted to a euthyroid state
Documented hypersensitivity; untreated thyrotoxicosis; untreated adrenal insufficiency; hyperfunctioning thyroid nodule
A - Fetal risk not revealed in controlled studies in humans
Caution in cardiac disease, arrhythmias, angina, and hypertension; elderly; prolonged subclinical hyperthyroidism is associated with bone loss and cardiac arrhythmias (monitor TSH q8-12wk)
Patients are monitored for hypothyroidism by history, examination, and TSH measurements. Initially, monitoring occurs every 6-8 weeks.
Benign euthyroid goiters do not require any medication. 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.
Triggiani V, Tafaro E, Giagulli VA, et al. Role of iodine, selenium and other micronutrients in thyroid function and disorders. Endocr Metab Immune Disord Drug Targets. Sep 1 2009;[Medline].
Tunbridge WM, Evered DC, Hall R, Appleton D, Brewis M, Clark F, et al. The spectrum of thyroid disease in a community: the Wickham survey. Clin Endocrinol (Oxf). Dec 1977;7(6):481-93. [Medline].
Sawin CT, Geller A, Hershman JM, Castelli W, Bacharach P. The aging thyroid. The use of thyroid hormone in older persons. JAMA. May 12 1989;261(18):2653-5. [Medline].
Guth S, Theune U, Aberle J, Galach A, Bamberger CM. Very high prevalence of thyroid nodules detected by high frequency (13 MHz) ultrasound examination. Eur J Clin Invest. Aug 2009;39(8):699-706. [Medline].
Duarte GC, Tomimori EK, de Camargo RY, Catarino RM, Ferreira JE, Knobel M, et al. Excessive iodine intake and ultrasonographic thyroid abnormalities in schoolchildren. J Pediatr Endocrinol Metab. Apr 2009;22(4):327-34. [Medline].
Pinchot SN, Al-Wagih H, Schaefer S, Sippel R, Chen H. Accuracy of fine-needle aspiration biopsy for predicting neoplasm or carcinoma in thyroid nodules 4 cm or larger. Arch Surg. Jul 2009;144(7):649-55. [Medline].
Arda IS, Yildirim S, Demirhan B, Firat S. Fine needle aspiration biopsy of thyroid nodules. Arch Dis Chil. 2001;85(4):313-7. [Medline].
Bardin CW. Endemic goiter. In: Current Therapy in Endocrinology and Metabolism. 6th ed. Mosby-Year Book; 1997:101-112.
Becker KL, Bilezikian JP, Bremner WJ. Nontoxic goiter. In: Principles and Practice of Endocrinology and Metabolism. 2nd ed. Lippincott Williams & Wilkins; 1995:338-345.
Bostanci I, Sarioglu A, Ergin H, Aksit A, Cinbis M, Akalin N. Neonatal goiter caused by expectorant usage. J Pediatr Endocrinol Metab. Sep-Oct 2001;14(8):1161-2. [Medline].
Braverman LE, Utiger RD. Thyroid diseases: nontoxic diffuse and multinodular goiter. In: Werner and Ingbar, eds. The Thyroid: A Fundamental and Clinical Text. 7th ed. Lippincott-Raven; 1996:889-900.
Gross JL. Ultrasonography in management of nodular thyroid disease. Annals of internal medicine. 2001;135(5):383-4. [Medline].
Romanchishen AF, Iakovlev PN. [Special surgical treatment of patients with nodular tumors of the thyroid gland against the background of diffuse toxic goiter]. Vestn Khir Im I I Grek. 2005;164(1):21-4. [Medline].
Sawin CT, Geller A, Wolf PA, et al. Low serum thyrotropin concentrations as a risk factor for atrial fibrillation in older persons. N Engl J Med. Nov 10 1994;331(19):1249-52. [Medline].
Schumm-Draeger PM. [Every third German has a sick thyroid gland. Nodules and goiter are a challenge that needs to be met]. MMW Fortschr Med. Feb 5 2004;146(6):20. [Medline].
Thompson L. Dyshormonogenetic goiter of the thyroid gland. Ear Nose Throat J. Apr 2005;84(4):200. [Medline].
Vetshev PS, Chilingaridi KE, Bannyi DA, Dmitriev EE. [Repeated surgeries on the thyroid gland in nodular euthyroid goiter]. Khirurgiia (Mosk). 2004;37-40. [Medline].
Wilson JD, Foster DW. The thyroid gland. In: Williams Textbook of Endocrinology. 8th ed. Harcourt Brace & Co; 1992:463-465.
goiter, goiter disease, thyroid disease, thyroid cancer, iodine deficiency, hypothyroidism, hyperthyroidism, thyroid nodules, thyroid gland goiter, nontoxic goiter, toxic goiter, multinodular goiter, endemic goiter, Hashimoto disease, iodine, enlarged thyroid gland, inborn errors of thyroid hormone synthesis, goitrogens, TSH receptor antibodies, pituitary resistance to thyroid hormone, adenomas of hypothalamus, adenomas of pituitary gland, tumors producing human chorionic gonadotropin, autoimmune thyroiditis, Hashimoto disease, swelling in the neck, Graves disease, Hashimoto thyroiditis
Riedel struma, toxic multinodular goiter, subacute thyroiditis, diffuse toxic goiter, toxic adenoma, Plummer disease, chronic lymphocytic thyroiditis, sporadic goiter, congenital goiter, physiologic goiter, Pemberton maneuver, postpartum thyroiditis, Wolff-Chaikoff effect, lithium ingestion, pituitary thyroid hormone resistance, thyroid-stimulating immunoglobulins, thyroid hormone resistance, de Quervain thyroiditis, silent thyroiditis, Riedel thyroiditis, granulomatous disease, thyroid malignancy
James R Mulinda, MD, FACP, FACE, Consulting Staff, Department of Endocrinology, Endocrinology Associates, Inc
James R Mulinda, MD, FACP, FACE is a member of the following medical societies: American College of Clinical Endocrinologists and American College of Physicians
Disclosure: Nothing to disclose.
Steven R Gambert, MD, MACP, Chairman, Department of Medicine, Physician-in-Chief, Sinai Hospital of Baltimore; Professor of Medicine, Program Director, Internal Medicine Program, Johns Hopkins University School of Medicine
Steven R Gambert, MD, MACP is a member of the following medical societies: Alpha Omega Alpha, American College of Physician Executives, American College of Physicians, American Geriatrics Society, Association of Professors of Medicine, Endocrine Society, and Gerontological Society of America
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment
Kent Wehmeier, MD, Professor, Department of Internal Medicine, Division of Endocrinology, Diabetes, and Metabolism, St Louis University School of Medicine
Kent Wehmeier, MD is a member of the following medical societies: American Society of Hypertension, Endocrine Society, and International Society for Clinical Densitometry
Disclosure: Nothing to disclose.
Mark Cooper, MBBS, PhD, FRACP, Head, Diabetes & Metabolism Division, Baker Heart Research Institute, Professor of Medicine, Monash University
Disclosure: Nothing to disclose.
George T Griffing, MD, Professor of Medicine, St Louis University School of Medicine
George T Griffing, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Medical Practice Executives, American College of Physician Executives, American College of Physicians, American Diabetes Association, American Federation for Medical Research, American Heart Association, Central Society for Clinical Research, Endocrine Society, International Society for Clinical Densitometry, and Southern Society for Clinical Investigation
Disclosure: Nothing to disclose.
I acknowledge my mentors for the foundations, my patients for their contributions to my knowledge, and my family for their patience.
Further ReadingClinical guidelines:
American Association of Clinical Endocrinologists and Associazione Medici Endocrinologi medical guidelines for clinical practice for the diagnosis and management of thyroid nodules.
American Association of Clinical Endocrinologists - Medical Specialty Society
Associazione Medici Endocrinologi - Medical Specialty Society. 1996 Jan (revised 2006 Feb). 40 pages. NGC:004869
Management guidelines for patients with thyroid nodules and differentiated thyroid cancer.
American Thyroid Association - Professional Association. 2006 Feb. 34 pages. NGC:005212
Screening for congenital hypothyroidism: U.S. Preventive Services Task Force reaffirmation recommendation statement.
United States Preventive Services Task Force - Independent Expert Panel. 1996 (revised 2008 Mar). 6 pages. NGC:006354
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