Thyroxine, also known as T4, is a hormone produced by the thyroid gland. It plays a crucial role in regulating metabolism, growth, and development in the body. Thyroxine helps control how the body uses energy, influencing various functions such as heart rate, temperature, and weight. In the bloodstream, thyroxine is converted into another hormone called triiodothyronine or T3, which is more active. Proper levels of thyroxine are essential for maintaining overall health, and imbalances can lead to conditions like hypothyroidism or hyperthyroidism, affecting energy levels and bodily functions.