A pilot study illuminates that high-dose vitamin D significantly improves lesions and depigmentation in psoriasis and vitiligo, respectively. Because Vitamin D deficiency is implicated in the pathophysiology of autoimmune responses, these findings may be applicable to other autoimmune disorders. Vitamin D: A Hormone Critical to Health Vitamin D insufficiency is a pandemic affecting nearly half of people worldwide, while one billion people are classified as vitamin D deficient. Hypovitaminosis D, or vitamin D deficiency, represents an independent predictor of total mortality in the general population, and conversely, vitamin D supplementation has been illustrated to be protective against mortality. Vitamin D enhances absorption of dietary calcium and phosphorus by 30-40% and 80%, respectively, but its physiological functions extend well-beyond mineral assimilation and balance. Vitamin D is known as a pleiotropic hormone, meaning that it elicits diverse and multi-faceted effects. In fact, local vitamin D production governs the expression of up to …