Thyroid Hormone impacts every major system in your body. It is important to have the right hormone levels for your body's needs. The function of the thyroid gland is to take iodine, found in many foods, and convert it into thyroid hormones: levothyroxine (T4) and liothyronine (T3). These thyroid hormones essentially control metabolism. Every cell in the body depends upon thyroid hormones for regulation of their metabolism. The Woodlands Compounding Pharmacy can work with your physician to make the best customized dose for you.