Diiodotyrisine (in short: DIT) is an endogenous amino acid which is as the intermediate product of the production of triiodothyronine (T3) and thyroxine (T4), which are endogenous thyroid hormones (due to iodine content). It affects the intensification of metabolism (it is a fat burner) and protein synthesis processes. Acts on the insulin activity. An ingredient of slimming supplements. Contraindication in use: use by minors and people suffering from hyperthyroidism, hypertension and neurologically treated. Because of regulations limiting its use by both WADA and the Polish law, it is slowly disappearing from sales on the domestic market.