Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone. This condition is often called underactive thyroid.
Myxedema; Adult hypothyroidism; Underactive thyroid; Goiter - hypothyroidism; Thyroiditis - hypothyroidism; Thyroid hormone - hypothyroidism
The thyroid gland is an important organ of the endocrine system. It is located at the front of the neck, just above where your collarbones meet. The thyroid makes hormones that control the way every cell in the body uses energy. This process is called metabolism.
Hypothyroidism 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:
Other causes of hypothyroidism include:
Late symptoms, if untreated:
The health care provider will do a physical exam and may find that your thyroid gland is enlarged. Sometimes, the gland is normal size or smaller-than-normal. The exam may also reveal:
You may also have tests to check:
Treatment is aimed at replacing the thyroid hormone you are lacking.
Levothyroxine is the most commonly used medicine:
When starting you on your medicine, your provider may check your hormone levels every 2 to 3 months. After that, your thyroid hormone levels should be monitored at least once every year.
When you are taking thyroid medicine, be aware of the following:
While you are taking thyroid replacement therapy, tell your provider if you have any symptoms that suggest your dose is too high, such as:
In most cases, thyroid hormone level becomes normal with proper treatment. You will likely take a thyroid hormone medicine for the rest of your life.
Myxedema crisis (also called myxedema coma), the most severe form of hypothyroidism, is rare. It occurs when thyroid hormone levels get very, very low. The severe hypothyroid crisis is then caused by an infection, illness, exposure to cold, or certain medicines (opiates are a common cause) in people with severe hypothyroidism.
Myxedema crisis is a medical emergency that must be treated in the hospital. Some people may need oxygen, breathing assistance (ventilator), fluid replacement, and intensive-care nursing.
Symptoms and signs of myxedema coma include:
People with untreated hypothyroidism are at increased risk of:
Call your provider if you have symptoms of hypothyroidism.
If you are being treated for hypothyroidism, call your provider if:
Brent GA, Weetman AP. Hypothyroidism and thyroiditis. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 13.
Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012;18(6):988-1028. PMID: 23246686 pubmed.ncbi.nlm.nih.gov/23246686/.
Jonklaas J, Bianco AC, Bauer AJ, et al; American Thyroid Association Task Force on Thyroid Hormone Replacement. Guidelines for the treatment of hypothyroidism: prepared by the American Thyroid Association task force on thyroid hormone replacement. Thyroid. 2014;24(12):1670-1751. PMID: 25266247 pubmed.ncbi.nlm.nih.gov/25266247/.
Reviewed By: Brent Wisse, MD, board certified in Metabolism/Endocrinology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.