Hypothyroidism: Fast Facts

Also known as underactive thyroid, hypothyroidism is a disorder in which the thyroid gland does not produce enough thyroid hormone to meet the body's needs.
Thyroid hormones are secreted by the thyroid gland, which is located in the neck.
Thyroid hormones help regulate a wide range of body functions, including growth and metabolism.
Hypothyroidism is most common in women over 50 but can also affect younger women, men and children.
The most common cause of hypothyroidism in the United States is a disease called Hashimoto's thyroiditis. This is an autoimmune disorder in which the body's immune system mistakenly attacks and inflames the thyroid gland. Additional possible causes include other forms of thyroiditis, pregnancy, pituitary disorders, iodine deficiency (rare in the United States), certain medications, certain genetic disorders and head injury.
Because the range of symptoms in hypothyroidism is so wide, it can be difficult for doctors to diagnose. Possible symptoms include fatigue, sluggishness, unexplained weight gain, puffiness in the face and ankles, personality changes, constipation and hoarseness.
Hypothyroidism is generally diagnosed with blood tests.
The majority of people with hypothyroidism will need to take manufactured versions of natural thyroid hormones for the rest of their lives to relieve their symptoms and to avoid serious long-term consequences.
Hypothyroidism can increase the risk for high cholesterol, hardening of the arteries, high blood pressure, heart disease, heart attack, stroke, anemia, cardiomegaly (enlarged heart), heart failure, respiratory problems, infertility and birth defects, and in severe cases a coma. Hypothyroidism in children can cause dwarfism.
Hypothyroidism should not be confused with hyperthyroidism, which is a condition marked by an abnormally high level of thyroid hormones in the blood. However, hyperthyroidism can sometimes result from treatments for hypothyroidism. The reverse is also true.
Pregnant women with hypothyroidism should be monitored closely. Pregnant women may require higher doses of thyroid hormone during pregnancy.
People who do not have hypothyroidism should not take medication intended for people with the condition. Synthetic thyroid hormone can be dangerous to people with normal thyroid function.

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