Vitamin D: A Pleiotropic Hormone with Possible Psychotropic Activities

After the recognition of the efficacy of cod-liver oil in rickets at the end of the eighteenth century, and the isolation and synthesis of the liposoluble vitamin D in 1931, its mode of actions and functions were deepened. Biochemical studies permitted to identify five forms of vitamin D, called D1, D2, D3, D4 and D5 differing in ultrastructural conformation and origin, with vitamin D2 (ergocalciferol) and D3 (cholecalciferol) representing the active forms. In the last decades especially, a constantly increasing bulk of data highlighted how vitamin D could regulate several activities and processes.