Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.
The thyroid gland is located in the front of the neck just below the voice box (larynx). It releases hormones that control metabolism. 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”)
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 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
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:
Lab tests to determine thyroid function include:
Other tests that may be done:
The purpose of treatment is to replace the thyroid hormone that is lacking. Levothyroxine is the most commonly used medication.
When starting your medication, your doctor may check your hormone levels every 2 – 3 months. After that, your thyroid hormone levels should be monitored at least every year.
Important things to remember when you are taking thyroid hormone:
While you are taking thyroid replacement therapy, tell your doctor if you have any symptoms that suggest your dose is too high, such as:
Myxedema coma is a medical emergency that occurs when the body’s level of thyroid hormones becomes very low. It is treated with intravenous thyroid hormone replacement and steroid medications. Some patients may need supportive therapy (oxygen, breathing assistance, fluid replacement) and intensive-care nursing.
In most cases, thyroid levels return to normal with proper treatment. However, you must take thyroid hormone replacement for the rest of your life.
Myxedema coma can result in death.
Thyroid crisis (storm) is a sudden worsening of hyperthyroidism symptoms that may occur with infection or stress. Fever, decreased mental alertness, and abdominal pain may occur. Immediate hospitalization is needed.
Other complications of hyperthyroidism include:
Treatments for hypothyroidism, such as radioactive iodine, surgery, and medications to replace thyroid hormones can have side effects.