The butterfly-shaped gland on the front of your neck, the thyroid, produces and secretes the hormones thyroxine and triiodothyronine (also known as T3) (also called T4). Too much thyroid hormone in the body is called thyrotoxicosis. About 2% of women and 0.2% of males in the United States have thyrotoxicosis. Graves' illness, which causes thyrotoxicosis, often manifests during the second and fourth decades of life. In contrast, toxic nodular goitre becomes more frequent with age. Medical experts use thyroid tests to evaluate the health of the thyroid and identify the root of thyroid disorders, including hyperthyroidism and hypothyroidism.
