They help generate heart rate, blood pressure, body temperature, and the rate at which food is converted into energy. The two main thyroid hormones are T3 (triiodothyronine) and T4 (thyroxine). The amount of thyroid hormones secreted is controlled by another hormone, called thyroid-stimulating hormone (TSH), which is released by the pituitary gland in the head (“How the Thyroid Works”). Thyroid hormones act throughout the body, influencing metabolism, growth, development and body temperature. During infancy and childhood, adequate thyroid hormone is critical for brain development (Tree, 2013). The thyroid gland also produces the hormone calcitonin, which is involved in calcium metabolism and stimulates bone cells to add calcium to the bones ("How the Thyroid Works")