What is the name of the condition where the thyroid gland is overactive?

The medical term for a thyroid gland that is overactive is hyperthyroidism.

The thyroid is a butterfly-shaped gland in the neck that releases the hormones thyroxine (T4) and triiodothyronine (T3). These hormones help regulate metabolism, heart rate, temperature and energy use. In hyperthyroidism, the gland produces too much hormone, accelerating many body processes.

Common effects include weight loss despite normal or increased appetite, heat intolerance, sweating, tremor, anxiety, muscle weakness, diarrhea and a rapid or irregular heartbeat. Graves’ disease, an autoimmune disorder, is the most frequent cause in many countries. Other causes include toxic thyroid nodules and thyroiditis.

Hyperthyroidism is not the same as goiter: a goiter is simply an enlarged thyroid and may occur with either excessive, normal or insufficient hormone production. Thyroiditis means inflammation of the gland; it can temporarily release stored hormone and produce hyperthyroid symptoms. Doctors typically confirm the condition with blood tests, especially low thyroid-stimulating hormone and elevated T4 or T3.