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Analyte: Vitamin D, 25-hydroxy
Specimen Type: Serum Inquire for additional option(s)
Optimum Volume: 0.5 mL
|7 days||1 year||3 years|
Reporting units: ng/mL
Biological or Clinical Significance:
Vitamin D, also known as caliciferal; is a group of fat-soluble secosteroids, the two major physiologically revlevant forms of which are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D without a subscript refers to either D2 or D3 or both.
Vitamin D3 is derived mainly from actions of ultraviolet light on the skin while D2 is derived solely from dietary sources. Since these two parent compounds provide various contributions to the overall vitamin D status of the individual, it is important that both forms are measured equally.
As (Vitamin D) enters the circulation, it is metabolized to several forms, the majority of these being 25-hydroxycalciferol (25-OH-D). The first step in the metabolism of vitamin D, 25-hydroxylation, occurs mainly in the liver. Only a small amount of 25-OH-D is metabolized in the kidney to other dihydroxyvitamin D metabolites. Since 25-OH-D is the predominant circulating form of vitamin D in the population, it is considered to be the most reliable index of vitamin D status.
The measurement of 25-OH-D is becoming increasingly important in the management of patients with various disorders of calcium metabolism associated with postmenopausal osteoporosis, neonatal hypocalcemia, pregnancy, nutritional and renal osteodystrophy, hypoparathyroidism, and rickets.
Principle of Test Method:
The 25-(OH) Vitamin D assay is a radioimmunoassay with sample extraction.
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