Key Features and Values
- Low limit of blank allowing measurement to very low concentrations of 25-OH D
- Wide measuring range allows assessment of insufficiency and toxic levels
- Supported by comprehensive panel of vitamin D and PTH assays for complete assessment of calcium metabolism
The 25-OH Vitamin D assay is intended for the quantitative determination of 25 hydroxyvitamin D in human serum or plasma and is intended for laboratory use only. Results are to be used in conjunction with other clinical and laboratory data to assist the clinician in the assessment of vitamin D sufficiency.
Vitamin D is a fat-soluble steroid pro-hormone. Of the two major forms Ergocalciferol (D2) and Cholecalciferol (D3), only vitamin D3 is synthesised by the body. Main vitamin D sources are: UV exposure from sun which leads to Cholecalciferol production in the upper layers of the skin, foods such as fish, shellfish, mushrooms, vitamin D fortified foods (e.g. milk, juice) and supplements. Approximately 10 – 20 % of vitamin D is supplied through nutritional intake.
Vitamin D is stored in adipose tissue and enters the circulation bound to vitamin D binding protein (VDBP) and albumin. In the liver, vitamin D is hydroxylated to give 25(OH)D which also circulates as a complex with VDBP. A small proportion of the 25(OH)D is further hydroxylated in the kidney, under direct regulation by parathyroid hormone and ionised calcium levels, to form the biologically-active calcitropic hormone 1,25-dihydroxyvitamin D [1,25(OH)2D]. Vitamin D plays a major role in calcium and phosphorus homeostasis.
Vitamin D deficiency is a cause of hyperparathyroidism and diseases related to impaired bone metabolism (e.g. rickets, osteoporosis, and osteomalacia).