Roughly 2 percent of American adults suffer hyperthyroidism. Most of them are women, who are 10 times more likely than men to have an overactive thyroid. Although not nearly as common in people over 50, an overactive thyroid gland (hyperthyroidism or thyrotoxicosis) is another potentially dangerous thyroid condition. Left untreated, hyperthyroidism can cause potentially fatal heart rhythm abnormalities and osteoporosis. Most cases of hyperthyroidism are caused by Graves’ disease, an autoimmune disorder characterized by an enlarged, overactive thyroid. Graves’ disease usually strikes during early adulthood or midlife. A common manifestation of Graves’ disease is bulging, watery eyes that feel gritty and are more sensitive to light. Graves’ disease may cause a
swollen neck (a goiter). Less commonly, hyperthyroidism is caused by the growth of a single lump or nodule that produces abnormally high amounts of thyroid hormone. While an underactive gland slows the body's metabolic rate, an overactive gland speeds it up by as much as 60 percent to 80 percent. Symptoms include: - weight loss
- fatigue
- nervousness
- insomnia
- shaking
- muscle weakness
- diarrhea
- heart palpitations
- increased sensitivity to light
- increased sweating
- intolerance to heat
- anxiety
- unusually light or absent menstrual periods
As with hypothyroidism, symptoms of hyperthyroidism can point to a number of disorders, and the disease can be easily missed, especially in older adults, who may not exhibit the symptoms that are characteristic of hyperthyroidism in younger people. Nevertheless, diagnosis can be made on the basis of low levels of TSH and T4 in a blood test. Hyperthyroidism is usually treated with radioactive iodine. As the thyroid absorbs the iodine, radiation destroys parts of the gland so that it produces less thyroid hormone. In about 50 percent of people, however, this renders the gland underactive, and patients then require lifelong T4 therapy. An overactive thyroid can also be treated with medications, such as propylthiouracil and methimazole (Tapazole), but their effectiveness is often limited to about a year. If the gland is unusually large, surgery is an option, but one that is rarely used. 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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