Abstract
Vitamin D is a fat-soluble molecule with pleiotropic effects, acting as a steroid hormone on three main organs: the intestine, bone, and kidney. Among its best-known functions at the skeletal level are regulating bone metabolism and mineralization. In 1983, the presence of vitamin D receptors on the surface of immune cells was described, which led to the discovery of new functions on immunological and inflammatory processes. Currently, we know that vitamin D modulates the adaptative immune system by suppressing cells that produce inflammatory cytokines by downregulation, acting as an important regulator of immunity and the inflammatory response. In this article, we will review the synthesis, metabolic pathways, and the role of vitamin D in rheumatic autoimmune diseases.