Thyroxine, commonly known as T4, is a hormone produced by the thyroid gland. It plays a crucial role in regulating metabolism, energy production, and overall growth and development in the body. T4 is primarily responsible for controlling how the body uses energy and influences various bodily functions, including heart rate and temperature. T4 is converted into another hormone called triiodothyronine (T3) in the body, which is more active and potent. The levels of T4 in the bloodstream are regulated by the pituitary gland through the release of thyroid-stimulating hormone (TSH). Proper levels of T4 are essential for maintaining good health and preventing conditions like hypothyroidism or hyperthyroidism.