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Hypothyroidism - Overview

Alternative Names

Myxedema; Adult hypothyroidism

Definition of Hypothyroidism:

Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.

Causes, incidence, and risk factors:

The thyroid gland is located in the front of the neck just below the voice box (larynx). It releases hormones that control metabolism.

The most common cause of hypothyroidism is inflammation of the thyroid gland, which damages the gland's cells. Autoimmune or Hashimoto's thyroiditis, in which the immune system attacks the thyroid gland, is the most common example of this. Some women develop hypothyroidism after pregancy (often referred to as "postpartum throiditis").

Other common causes of hypothyroidism include:

Congenital (birth) defects
Radiation treatments to the neck to treat different cancers, which may also damage the thyroid gland
Radioactive iodine used to treat an overactive thyroid (hyperthyroidism)
Surgical removal of part or all of the thyroid gland, done to treat other thyroid problems
Viral thyroiditis, which may case hyperthyroidism and is often followed by temporary or permanent hypothyroidism

Certain drugs can cause hyperthyroidism, including:

Amiodarone
Drugs used for hyperthyroidism (overactive thyroid), such as propylthiouracil (PTU) and methimazole
Lithium
Radiation to the brain
Sheehan syndrome, a condition that may occur in a woman who bleeds severely during pregnancy or childbirth and causes destruction of the pituitary gland

Risk factors include:

Age over 50 years
Being female

Reviewed last on: 4/29/2009
Deborah Wexler, MD, Assistant Professor of Medicine, Harvard Medical School, Endocrinologist, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

References

Fatourechi V. Subclinical hypothyroidism: an update for primary care physicians. Mayo Clin Proc. 2009;84(1):65-71.

Ladenson P, Kim M. Thyroid. In: Goldman L and Ausiello D, eds. Goldman: Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders; 2007:chap 244.

Vaidya B, Pearce SH. Management opf hypothyroidism in adults. BMJ. 2008;28;337:a801.

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