Thyroid hormones and their metabolites: biological roles and association with non-alcoholic fatty liver disease

Thyroid hormones (THs) and their metabolites are potent regulators of energy and lipid metabolism in the liver. Besides the physiological role of THs in liver cell homeostasis, thyroid dysfunctions have been shown to play an essential part in the onset and progression of some liver diseases. Among these, non-alcoholic fatty liver disease (NAFLD), the current leading reason of development of chronic liver diseases worldwide, has emerged. In the present review, we analyse the main biological activities of THs and of some of their metabolites, along with their mechanisms of action, focusing on their role as master regulators of energy metabolism. We describe the relationship between thyroid dysfunctions and the development of NAFLD. Finally, we underline how the study of THs and their metabolites might be useful to develop new therapeutic approaches for NAFLD.