In hyperthyroidism, the thyroid gland is overactive. It produces too much of its hormone. Hyperthyroidism affects about 1% of women. It’s less common in men.
Graves’ disease is the most common cause of hyperthyroidism, affecting about 70% of people with an overactive thyroid. Nodules on the thyroid — a condition called toxic nodular goiter or multinodular goiter — can also cause the gland to overproduce its hormones.
Excessive thyroid hormone production leads to symptoms such as:
- racing heart
- increased sweating
- trouble sleeping
- thin skin
- brittle hair and nails
- muscle weakness
- weight loss
- bulging eyes (in Graves’ disease)