CLINICAL MASS SPECTROMETRY SERVICES

Vitamin D estimation LC MS/MS

Vitamin-D and parathyroid hormone (PTH) are the principle regulators of calcium homeostasis in all tetrapods and play an important role in bone metabolism

Vitamin-D exists in two major forms, vitamin-D2 (ergocalciferol) and vitamin-D3 (cholecalciferol). Both are formed by UV irradiation of either 7-dehydroergosterol (phytoplankton, fungi and yeast) or 7-dehydrocholesterol (all vertebrates with the exception of fish [predominately dietary-derived vitamin-D2]). The two forms differ only in the substitution on the side chain.

In modern humans, primary sources of vitamin-D include diet or supplements (vitamin-D2 and/or-D3) and vitamin-D3 derived from 7-dehydrocholesterol in the skin after exposure to UV light. Since vitamin-D3 and vitamin-D2 are either stored in adipose tissue or rapidly metabolized to the corresponding 25-hydroxylated metabolites, their serum levels fluctuate widely and there is no clinical value in monitoring these forms of vitamin-D in the circulation.

Among the >40 vitamin-D metabolites discovered so far, three have been shown to be the most clinically relevant: 25(OH)D, 1,25(OH)2D and 24,25(OH)2D.

Methodologies for 25(OH)D measurements include high performance liquid chromatography (HPLC), radioimmunoassay (RIA), automated immunoassays and liquid chromatography-tandem mass spectrometry (LC-MS/MS), while current 1,25(OH)2D and 24,25(OH)2D measurements involve RIAs or LC-MS/MS. Analytical challenges have been reported for all of these methods (Singh, 2008), but currently measurement of vitamin-D compounds by HPLC with MS/MS detection (Heijboer et al., 2012; Eisman and Deluca, 1978) has been established as the gold standard for vitamin-D metabolite testing

LC-MS/MS overcomes these analytical challenges and has become widely accepted for routine use for many low molecular weight analytes in clinical laboratories due to improved analytical specificity and sensitivity and wider dynamic range compared to immunoassay methods

What is the recommended level of vitamin D?

The recommended blood levels of vitamin D – is more than 30ng/ml