The thyroid gland produces two thyroid hormones, triiodothyronine (T3) and thyroxine (T4), and releases them as needed by the body. The hypothalamus and the pituitary gland help control the thyroid gland. The hypothalamus produces thyrotropin-releasing hormone (TRH), which stimulates the pituitary gland to release thyroid-stimulating hormone (TSH). A low level of T3 tells the hypothalamus to release more TRH, and it tells the pituitary to release more TSH. The thyroid gland releases T3 and T4 until the body is receiving the required amount.