T3 is a thyroid hormone commonly used for weight (fat) loss, particularly in the context of anabolic steroid cycles. T3 is produced naturally in the body in response to the production of T4 (thyroxine) by the thyroid gland.
Oral administration of T3 can lead to an abnormal increase in serum T3 concentrations, enabling more rapid fat loss and, in some cases, potentially greater GH production and higher anabolism.