Serum 25-hydroxy vitamin D levels in essential hypertension

For decades 25(OH) vitamin D has been considered a dynamic steroid hormone exerting its action as a transcription factor regulating the expression of various genes (1). Vitamin D is a cluster of fat-soluble molecules analogous to steroids. Numerous forms of vitamin D exist; cholecalciferol (or vitamin D3) is synthesized in reaction to ultraviolet (UV) irradiation of the skin consequential to the photochemical cleavage of 7-dehydrocholesterol, a precursor of cholesterol in the skin. A second form of vitamin D, ergocalciferol (or vitamin D2) is formed by irradiation of ergosterol, a membrane sterol found in the Ergot fungus. Nutritional sources of vitamin D comprise fish oils (D3), egg yolks (D3), and mushrooms (D2) as well as unnaturally prepared cereals and dairy products (D2 or D3). Epidemiological studies then established improved risks of chronic morbid disorders with lower levels of serum 25-OH D. More recently, 25(OH) vitamin D deficiency has been considered as an independent risk factor for cardiovascular disease and mortality in general population. Biologic effects of 25(OH) vitamin D result largely from its binding to the nuclear steroid hormone 25(OH) vitamin D receptor (VDR), which is found in almost all tissues and is moreover closely related to the thyroid, retinoid, and peroxisome proliferator-activator receptors. While all 25(OH) vitamin D metabolites bind the VDR, most biological effects are probable mediated by calcitriol because of its greater receptor similarity (2). Vitamin D plays a considerable function in the physiology of the cardiovascular system and its insufficiency has been allied to extensive complications, such as cardiovascular events, hypertension, obesity, metabolic syndrome, type 2 diabetes, immune disorders and numerous types of cancer (3,4). The indisputable potential inverse relationship between vitamin D deficiency and elevated blood pressure (BP) suggests involvement of vitamin D metabolism in the pathogenesis of hypertension.