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Vitamin D2 (ergocalciferol)

Vitamin D is an important agent for the control of the calcium and phosphate balance in an organism, and the regulation of bone formation. It is activated by 25-hydroxylation in the liver and subsequently by 1-hydroxylation in the kidney. This stimulates intestinal calcium transport, the mobilization of calcium from bone, and an increased reabsorption of calcium in the kidney. The production of the final form of vitamin D, 1,25-dihydroxy vitamin D, is regulated by the need for calcium and phosphorus. Vitamin D2, which is refined from vitamin D1 containing other isomers and is highly antirachitic, and vitamin D3 are often used today for the treatment of patients suffering from rickets, osteomalacia, osteoporosis, osteatis fibrosa, osteosclerosis and other bone diseases, malignant tumors such as breast and colon cancers, and skin diseases such as psoriasis. In general, vitamin D by itself is used to refer to highly antirachitic vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) are the two important nutritional forms of vitamin D out of all the known forms of vitamin D. Provitamin D3 (7-dehydrocholesterol) exists in the skin of animals, while provitamin D2 (ergosterol) exists in plants and in many lower organisms, such as fungi and yeasts. Provitamins D2 and D3 are converted into their corresponding vitamins D2 and D3 when exposed to UV radiation. The two vitamins differ only in the structure of their side chains. While vitamin D3 is the only endogenous form of vitamin D in human skin, both vitamins D2 and D3 are metabolized identically and have equivalent biological potency in most mammals. Historically, vitamin D2 became important medicine as it was the first synthetic vitamin D preparation available for the treatment of rickets, and it is still being widely used to satisfy both therapeutic and nutritional needs of man and other commercially important mammals.

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