Thyroid hormones are hormones produced by the thyroid gland that regulate metabolism. The two main hormones produced by the thyroid are thyroxine (T4) and triiodothyronine (T3). T4 is the main hormone produced by the thyroid, and it is converted to the active form T3 in other parts of the body. T3 is three to four times more active than T4. These hormones control the body’s energy use and metabolism, and also play a role in regulating body temperature, heart rate, and other bodily functions. Deficiency or excess of these hormones can lead to various thyroid disorders such as Hypothyroidism and Hyperthyroidism.