| Intended use |
Vitamin D is a steroid hormone involved in the intestinal absorption of calcium and the regulation of calcium homeostasis. There are two different forms of Vitamin D, named D3 and D2, which are very similar in structure. The Vitamin D2 is a synthetic product, which is predominantly absorbed by fortified food. Physiological Vitamin D3 levels result not only from dietary uptake but can also be produced from a cholesterol precursor, 7-dehydrocholesterol, in the skin during sun exposure. In the liver, the vitamin is hydroxylated to 25-hydroxyvitamin D (25-OH-Vitamin D), the major circulating metabolite of Vitamin D. Although 1,25-(OH)2 Vitamin D portrays the biological active form of Vitamin D, which is synthesized in the kidney, it is widely accepted that the measurement of circulating 25-OH-Vitamin D provides better information with respect to patients Vitamin D status and allows its use in diagnose hypovitaminosis. The concentration of 25-OH-Vitamin D decreases with age and a deficiency is common among elderly persons. Clinical applications of 25-OH-Vitamin D measurements are the diagnosis and therapy control of postmenopausal osteoporosis, rickets, osteomalacia, renal osteodystrophy, pregnancy, neonatal hypocalcemia and hyperparathyroidism. In addition, a prevalence of subclinical Vitamin D deficiency has been discussed in different European countries. Vitamin D intoxication mostly occurs during a large intake of pharmaceutical preparations of Vitamin D and may lead to hypercalcemia, hypercalcuria and nephrocalcinosis in susceptible infants. |
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25-OH-Vitamin D direct
