The most common cause of hyperthyroidism is the autoimmune disorder Graves’ disease. In this disorder, the body makes an antibody (a protein produced by the body to protect against a virus or bacteria) called thyroid-stimulating immunoglobulin (TSI) that causes the thyroid gland to make too much thyroid hormone. Graves’ disease runs in families and is more commonly found in women.
Hyperthyroidism also may be caused by a toxic nodular or multinodular goiter, which are lumps or nodules in the thyroid gland that cause the thyroid to produce excessive amounts of thyroid hormones. In addition, inflammation of the thyroid gland—called thyroiditis—resulting from a virus or a problem with the immune system may temporarily cause symptoms of hyperthyroidism. Furthermore, some people who consume too much iodine (either from foods or supplements) or who take medications containing iodine (such as amiodarone) may cause the thyroid gland to overproduce thyroid hormones.
Finally, some women may develop hyperthyroidism during pregnancy or in the first year after giving birth. What are the symptoms of hyperthyroidism?
- Fatigue or muscle weakness
- Hand tremors
- Mood swings
- Nervousness or anxiety
- Rapid heartbeat
- Heart palpitations or irregular heartbeat
- Skin dryness
- Trouble sleeping
- Weight loss
- Increased frequency of bowel movements
- Light periods or skipping periods
- Frequent bowel movement—perhaps diarrhea
- Heat intolerance
- Increased sweating
Some people may develop a goiter, which is an enlarged thyroid gland that feels like a swelling in the front of your neck. When you have hyperthyroidism, your body is producing excessive amounts of the thyroid hormones T3 and T4. Since these hormones regulate your metabolism (how your body processes and uses energy), having too high a level will cause symptoms related to a high metabolism. In essence, hyperthyroidism speeds up some of your body's processes.