The role of vitamin D in melanogenesis with an emphasis on vitiligo

Vitiligo is a common pigmentary disorder caused by the destruction of functional melanocytes.Vitamin D is an essential hormone synthesized in the skin and is responsible for skin pigmentation.Low levels of vitamin D have been observed in vitiligo patients and in patients with other autoimmune diseases.Therefore, the relationship between vitamin D and vitiligo needs to be investigated more thoroughly.We reviewed the literature to date regarding the role of vitamin D in skin pigmentation.Our review revealed that vitamin D defi ciency has been identifi ed in many conditions, including premature and dysmature birth, pigmented skin, obesity, advanced age, and malabsorption.Vitamin D increases melanogenesis and the tyrosinase content of cultured human melanocytes by its antiapoptotic effect.However, a few growth-inhibitory effects on melanocytes were also reported.Vitamin D regulates calcium and bone metabolism, controls cell proliferation and differentiation, and exerts immunoregulatory activities.Vitamin D exerts its effect via a nuclear hormone receptor for vitamin D. The topical application of vitamin D increased the number of L-3,4-dihydroxyphenylalanine-positive melanocytes.The topical application of vitamin D yields signifi cant results when used in combination with phototherapy and ultraviolet exposure to treat vitiligo in humans.Vitamin D decreases the expression of various cytokines that cause vitiligo.In conclusion, application of vitamin D might help in preventing destruction of melanocytes thus causing vitiligo and other autoimmune disorders.The association between low vitamin D levels and the occurrence of vitiligo and other forms of autoimmunity is to be further evaluated.