3,3′,5’-Triiodo-L-thyronine (Reverse T3), is a thyroid hormone generated by the deiodination of the prohormone thyroxine. It is about 1,000-fold less active at the thyroid hormone receptors TRα and TRβ than 3,3′,5-triiodo-L-thyronine.  Reverse T3 positively regulates the hepatic FGF21 expression and stimulates the metabolic breakdown of glucose, fats, and proteins by enhancing the levels of numerous metabolic enzymes such as hexokinase, liver glucose 6-phosphatase as well as mitochondrial enzymes for oxidative phosphorylation.