25(OH)-Vitamin D dried blood (dried blood samples), ELISA

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 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 is 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 (1,2).
Preanalytical stability of 25(OH)-vitamin D3
in human blood or serum at room temperature:
solid as a rock (Wielders and Wijnberg, 2009).
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.