Women are 10 times more likely to suffer from hypothyroidism than men, and an estimated 8 percent to 10 percent of women over age 50 have an underactive thyroid. The condition is most frequently caused by Hashimoto's thyroiditis, an autoimmune disorder that prompts the body's immune system to attack the thyroid gland. In addition, previous thyroid surgery or radioactive iodine treatment can lead to an underactive thyroid. Too little iodine in the diet was once a major cause, but the introduction of iodized salt in the 1920s has practically eradicated this problem in the United States. Finally, certain medications such as lithium (prescribed to treat manic-depressive disorder) and the anti-arrhythmic drug amiodarone (Cordarone), and radiation treatment for disorders such as Hodgkin's disease or throat cancer can also cause hypothyroidism. A mildly underactive thyroid (subclinical hypothyroidism) may be asymptomatic, but each year about 5 percent of patients with subclinical hypothyroidism progress to overt hypothyroidism, in which symptoms surface. Symptoms include: - weight gain
- fatigue
- constipation
- sensitivity to cold
- depression
- impaired memory
- dry, brittle hair or hair loss
- decreased sex drive
- dry skin
- hoarseness
- muscle cramps
A simple test that measures the amount of TSH in the blood can confirm or rule out an underactive thyroid. TSH levels are elevated in patients with overt hypothyroidism and in those whose thyroid gland is only mildly underactive. However, in rare cases, hypothyroidism is due to a disorder of the pituitary, and TSH levels are not high in these people. It is important to treat hypothyroidism even when it does not cause symptoms. An underactive thyroid gland, even a mild one, can be associated with high cholesterol, and thus is a risk factor for heart disease. Treating the condition can reverse elevated cholesterol levels and halt the progression to overt heart disease. Most people with hypothyroidism require daily, lifetime therapy with synthetic T4 (or levothyroxine sodium, marketed under the brand names Levothroid, Synthroid, Levoxyl and Eltroxin). Although T4 therapy is safe and effective, an abrupt increase in T4 levels may increase the demand for oxygen by the heart, which could lead to a heart attack, particularly in older people. Therefore, T4 treatment should be started at a low dose and gradually increased until T4 and TSH are in the normal range. Last Updated: 2/6/2003
The Johns Hopkins University 1996-2003. All rights reserved. This information is not intended to provide advice on personal medical matters, nor is it intended to be a substitute for consultation.
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