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

Causes

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

Hypothyroidism, or underactive thyroid, is more common in women and people over age 50.

The most common cause of hypothyroidism is thyroiditis. Swelling and inflammation damage the thyroid gland's cells. Causes of this problem include:

An attack of the thyroid gland by the immune system

Cold or other respiratory infection

Pregnancy (often called "postpartum thyroiditis")

Other causes of hypothyroidism include:

Certain drugs, such as lithium and amiodarone

Congenital (birth) defects

Radiation treatments to the neck or brain to treat different cancers

Radioactive iodine used to treat an overactive thyroid gland

Surgical removal of part or all of the thyroid gland

Sheehan syndrome, a condition that may occur in a woman who bleeds severely during pregnancy or childbirth and causes the destruction of the pituitary gland

Symptoms

Early symptoms:

Hard stools or constipation

Increased sensitivity to cold

Fatigue or feeling slowed down

Heavier menstrual periods

Joint or muscle pain

Paleness or dry skin

Sadness or depression

Thin, brittle hair or fingernails

Weakness

Weight gain without trying

Late symptoms, if left untreated:

Decreased taste and smell

Hoarseness

Puffy face, hands, and feet

Slow speech

Thickening of the skin

Thinning of eyebrows

Exams and Tests

A physical examination may reveal a smaller-than-normal thyroid gland, although sometimes the gland is normal size or even enlarged (goiter). The examination may also reveal: