Vitamin D3 (Cholecalciferol): Metabolism, Functions, and Role in Disease

Abstract

Background: Vitamin D3 (cholecalciferol) is a fat-soluble vitamin essential for calcium homeostasis, bone metabolism, and various extra-skeletal functions. It is primarily synthesized in the skin under ultraviolet B (UVB) radiation and undergoes sequential hydroxylation in the liver and kidneys to form its active metabolite, calcitriol. Beyond its classical role in bone health, vitamin D3 has been implicated in multiple physiological processes including immune modulation, cellular proliferation, and cardiovascular regulation. Emerging evidence suggests its involvement in the pathogenesis and progression of several chronic diseases such as cardiovascular disorders, cancer, and osteoporosis.