Graves’ Disease

source: American Association for Clinical Chemistry (AACC)

Graves disease is the most common cause of overactive thyroid (hyperthyroidism). It is an autoimmune disorder, an attack on the thyroid gland by a person’s own immune system. The thyroid gland is a butterfly-shaped organ that lies flat against the windpipe in the throat. It produces the hormones thyroxine (T4) and triiodothyronine (T3) and plays an important role in controlling the body’s metabolism.

Thyroid hormone production is normally regulated in a feedback mechanism that includes the pituitary gland, a pea-sized organ at the base of the brain. The pituitary produces thyroid-stimulating hormone (TSH), which in turn stimulates the production of T4 and T3. With Graves disease, an autoantibody called thyroid stimulating immunoglobulin (TSI) is produced. TSI acts like TSH and causes the thyroid gland to produce excess thyroid hormone. Over time, this can cause the thyroid gland to enlarge.