Hyperthyroidism is overactivity of the thyroid gland.
Too much thyroid hormone is produced and released into the body. The excess thyroid hormone speeds up most chemical reactions in the body, causing mental and physical changes. To diagnose hyperthyroidism, the doctor will ask about your symptoms, examine you, and order lab tests. Some of these tests measure hormone levels and others check thyroid gland function. The doctor may order other tests such as a thyroid scan and an ultrasound.