Hyperthyroidism affects about the same percentage of older people as younger people—about 1%. However, hyperthyroidism is often more serious among older people because they tend to have other disorders as well.
Hyperthyroidism in older people often results from Graves disease. Almost as often, hyperthyroidism is caused by the gradual growth of many small lumps in the thyroid gland (toxic thyroid nodules).
Some medications can cause hyperthyroidism as well. The most common is amiodarone, a medication used to treat heart disease but which may stimulate or damage the thyroid gland.
Hyperthyroidism can cause many vague symptoms that can be attributed to other conditions. Typically, symptoms are different in older and younger people.
Among older people, the most common symptoms are weight loss and fatigue. The heart rate may or may not be increased, and the eyes usually do not bulge. Older people are also more likely to have abnormal heart rhythms (such as atrial fibrillation), other heart problems (such as angina and heart failure), and constipation.
Occasionally, older people sweat profusely, become nervous and anxious, and have hand tremors and frequent bowel movements or diarrhea.