What is hyperthyroidism?
Hyperthyroidism happens when the thyroid gland makes more hormone than the body needs, revving up heart rate, body temperature and calorie burn. Most cases are caused by Graves' disease, in which antibodies keep stimulating the thyroid; toxic nodules and thyroiditis are other causes (Ross et al., 2016). The opposite condition is hypothyroidism.
What are the symptoms, and how is it diagnosed?
Common signs are unintended weight loss despite a good appetite, a pounding or racing heart, heat intolerance and sweating, shaky hands, anxiety and trouble sleeping. Graves' disease can also cause bulging, irritated eyes (thyroid eye disease). Blood tests showing a low TSH with high free T4 or T3 confirm it; antibody tests and a thyroid uptake scan pinpoint the cause. In older adults it may first show up as atrial fibrillation.
How is it treated?
US options include antithyroid drugs (methimazole), radioactive iodine—historically the most common US choice—and thyroidectomy. Beta-blockers ease the racing heart while other treatments take effect. If you're on methimazole and develop a fever or sore throat, call your doctor right away to rule out a rare drop in white blood cells.
This article is general health information and is not a substitute for diagnosis or treatment. If symptoms persist, see a doctor.
FAQ
- Is hyperthyroidism curable?
- Many people reach remission or a permanent fix, but radioactive iodine and surgery usually lead to hypothyroidism that's managed with daily levothyroxine.
- Can stress cause hyperthyroidism?
- Stress doesn't directly cause it, but it may trigger Graves' disease in people who are already predisposed.
Sources reviewed: 2026-10-25
References
- Ross, D. S., Burch, H. B., Cooper, D. S., et al. (2016). 2016 American Thyroid Association guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis. Thyroid, 26(10), 1343–1421.
- Smith, T. J., & Hegedüs, L. (2016). Graves' disease. New England Journal of Medicine, 375(16), 1552–1565.