Thyroid Gland Health Article

Hyperthyroidism

Hyperthyroidism results from an excess amount of T4 and T3 in the blood stream. The major symptoms of hyperthyroidism include nervousness, tremors, sweating,

heat intolerance, palpitations, weight loss with normal caloric intake, amenorrhea, and muscle weakness. In the presence of clinical symptoms the diagnosis of hyperthyroidism can be confirmed when serum measurements indicate increased T4 and/or decreased TSH levels. Hyperthyroidism can be treated through medications such as thionamides, which inhibit the synthesis of T4 and T3, and beta blockers which block the action of thyroid hormones on peripheral cells. Patients who cannot be treated through medications are treated through radioiodine destruction of the thyroid or surgical removal of the thyroid. Surgical removal of the thyroid and sometimes radioiodine treatment can leave the patient permanently hypothyroid.

GRAVES' DISEASE. Graves' disease, the most common cause of hyperthyroidism, is an autoimmune disease resulting from the formation of antibodies against the TSH receptors in the thyroid gland. The only difference between Hashimoto's thyroiditis and Graves' disease is that Graves disease results when these antibodies stimulate thyroid hormone synthesis rather than inhibiting it. Graves' disease results in increased synthesis of T4 and T3, and can result in exophthalmos, thyroid enlargement and goiter, and vitilago. People with Graves' disease may pass on a genetic predisposition and a slightly increased chance of developing Graves' disease to their offspring.

KEY TERMS

Adenoma—A benign glandular epithelial tumor.

Autosomal dominant—Mutation of only one gene of a pair is required to cause abnormal functioning.

Autosomal recessive—Mutations in both genes of a pair are required to cause abnormal functioning.

Basal metabolic rate—The number of calories that the body consumes when at rest.

Bradycardia—Slowing of the pulse.

Colloid—The gelatinous material made up primarily of thyroglobulin which is found in the follicles of the thyroid.

Cardiac contractility—The ability of the muscles of the heart to contract in the presence of a stimulus.

Endocrine system—A group of organs that secrete hormones directly into the circulatory system that affect metabolism and other body functions.

Exophthalmos—Protrusion of the eyeball.

Goiter—An enlarged thyroid gland resulting in a swelling on the front of the neck.

Hemangioma—Benign tumor made of newly formed blood vessels.

Hormone—A chemical produced by the body which is involved in regulating specific bodily functions such as growth, development, and reproduction.

Hormonogenesis—The production of hormones.

Lobe—Well defined segment of an organ.

Metabolism—Activity by which cells obtain energy from nutrients or use energy to perform basic body functions.

Thyroglobulin—Protein found in the follicles of the thyroid which is involved in the formation of the T4 and T3 hormones produced by the thyroid.

Trachea—Windpipe.

Vitiligo—A skin disorder characterized by depigmented white patches that can have a hyperpigmented border.

OTHER CAUSES OF HYPERTHYROIDISM. Toxic adenoma of the thyroid results from a thyroid nodule that produces additional T4 and T3. This excess production of thyroid hormones results in increased concentrations of T3 and/or T4 in the blood stream and suppression of TSH. Toxic adenoma can be treated through surgical removal of the thyroid, treatment with radioactive iodine, and injection of ethanol into the nodule.

Hyperthyroidism can also be caused by a toxic multinodular goiter. Toxic multinodular goiter is common in areas of iodine deficiency. The multinodular goiter usually results from a goiter caused by hypothyroidism which eventually develops multiple nodules. These nodules produce excess T4 and T3 hormone independent of the TSH levels. Treatment usually involves radioactive iodine or surgery. Hyperthyroidism can also occasionally be caused from abnormalities such as adenomas of the pituitary gland which result in an increased production of TSH. Infections of the thyroid gland can also result in hyperthyroidism. Uncontrolled maternal hyperthyroidism in pregnancy can cause hyperthyroidism in the fetus. In the past hyperthyroidism was occasionally induced when individuals ingested hamburgers containing ground up bovine thyroid gland.

BOOKS

Braverman, L. E., and R. D. Utiger, eds. The Thyroid: A Fundamental and Clinical Text. Philadelphia, PA: Lippincott Williams and Wilkins, 2000.

Falk, S.A., ed. Thryoid Disease: Endocrinology, Surgery, Nuclear Medicine and Radiotherapy. 2nd edition. Philadelphia, PA: Lippincott-Raven, 1997.

Fisher, D. A. "Thyroid Disorders." In Principles and Practice of Medical Genetics. Edited by D. L. Rimoin, J. M. Connor, and R. E. Dyeritz. New York: Churchill Livingstone, 1997, pp.1365–1377.

ORGANIZATIONS

The American Thyroid Association, Inc. Townhouse Office Park, 55 Old Nyack Turnpike, Suite 611, Nanuet, NY 10954. Fax: 914–623–3736. <http://www.thyroid.org/>.

OTHER

American Association of Clinical Endocrinology (AACE). Clinical Practice Guidelines for Evaluation and Treatment of Hyperthyrodism and Hypothyroidism. <http://www.aace.com/clin/guides/thyroid_guide.html>(1996).

De Groot, Leslie J and, Georg Hennemann. (eds.) The Thyroid Manager. <http://www.thyroidmanager.org/> (February 1,2001).

Lisa Maria Andres, M.S., CGC