HYPOTHYROIDISM

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Endocrine glands

Hypothyroidism

Brain-thyroid link

Thyroid gland

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Definition

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

See also:

• Chronic thryoiditis (Hashimoto's disease)
• Subacute thyroiditis
• Silent thyroiditis
• Neonatal hypothyroidism

Alternative Names

Myxedema; Adult hypothyroidism

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

Symptoms

Early symptoms:

• Being more sensitive to cold
• Constipation
• Depression
• Fatigue or feeling slowed down
• Heavier menstrual periods
• Joint or muscle pain
• Paleness or dry skin
• Thin, brittle hair or fingernails
• Weakness
• Weight gain (unintentional)

Late symptoms, if left untreated:

• Decreased taste and smell
• Hoarseness
• Puffy face, hands, and feet
• Slow speech
• Thickening of the skin
• Thinning of eyebrows

Reviewer Info: 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., 04/29/2009