Measurement of 25-hydroxyvitamin vitamin D by liquid chromatography tandem-mass spectrometry with comparison to automated immunoassays.

摘要

There are two forms of vitamin D: vitamin D_2 and vitamin D_3. These two forms are metabolized in the liver to give 25-hy-droxyvitamin D (25-OHD), then hydrolyzed in the kidney to 1,25-dihydroxyvitamin D (1,25-OHD), the biologically active metabolite. Thus, the serum concentration of the two 25-OHD metabolites is now considered a reliable measure of vitamin D status. Vitamin D deficiency was associated with lower bone density, muscle disorders, heart and circulatory diseases, nervous system disorders (1) and diabetes (2). Hypovitaminosis D is associated with decreased serum calcium, leading to increased blood concentration of parathyroid hormone (PTH). Consequently, increased PTH may indicate mild normocalcemic forms of vitamin D deficiency. Although there is still no consensus on 25-OHD serum concentration below which vitamin D insufficiency is defined, there is agreement that 30 ng/mL 25-OHD is the cut-off value for defining optimal vitamin D status as this value induces PTH suppression (3).