Conditions InDepth: Hyperthyroidism
Hyperthyroidism is a condition in which the body has too much thyroid hormone in the blood. Thyroid hormone is made by the thyroid gland, a butterfly-shaped gland in the front of the neck. It produces the hormones thyroxine (T4) and triiodothyronine (T3), which control metabolism. This affects:
- How many calories you burn
- How warm you feel
- How much you weigh
- How the body handles many other vital functions of the cardiovascular, gastrointestinal, and nervous systems—Thyroid hormones directly affect the heart. If you have too much thyroid hormones in your blood, it will cause your heart to beat harder and faster.