Vitamin D is a fat-soluble vitamin that is involved in calcium-phosphorus metabolism. It exists in two forms: cholecalciferol (Vitamin D3), and ergocalciferol (Vitamin D2). In the bloodstream D2 and D3 are conjugated
Vitamin D is a fat-soluble vitamin that is involved in calcium-phosphorus metabolism. It exists in two forms: cholecalciferol (Vitamin D3), and ergocalciferol (Vitamin D2). In the bloodstream D2 and D3 are conjugated to carrier proteins, mainly VDBP (Vitamin D-Binding Protein). Both the forms are biologically inert and suffer, in the body, two important hydroxylations: the first in the liver, with formation of calcidiol (25(OH) Vitamin D); the second in the kidney, with the formation of calcitriol (1.25(OH)2 Vitamin D), the biologically active metabolite.
25(OH) Vitamin D is generally considered the main form of storage and the determination of its serological concentration is considered a reliable indicator of overall Vitamin D status (more than 95% of Vitamin D in the serum is represented by 25(OH)).
Vitamin D is essential for good health of bones. A deficiency of Vitamin D results in a defective mineralization of the bone structure which can lead to childhood rickets, osteoporosis and osteomalacia in adults. An excess of Vitamin D, "Hypervitaminosis D" determines pathological effects on the organism.
Vitamin D has also extra-skeletal functions, including the immune modulating and anti-proliferative, has a possible role in chronic inflammatory and neoplastic diseases, diabetes, cardiovascular and autoimmune diseases and in dermatology, where a deficiency of Vitamin D is associated to psoriasis, vitiligo, atopic dermatitis, melanoma and epithelial tumors of the skin.
Several studies have shown that, in Mediterranean countries such as Italy, despite the latitude, the population is among those with the lowest serum levels of Vitamin D in Europe.
