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THE GENERATION DIAGNOSTIC SYSTEM
Vitamin D from the diet or dermal synthesis from sunlight is biologically inactive and is a fat soluble steroid hormone involved in the active intestinal absorption of calcium and in the regulation of its homeostasis. In humans, the most important compounds in this group are vitamin D3 (also known as cholecalciferol) and vitamin D2 (ergocalciferol). In the liver, cholecalciferol (vitamin D3) is converted to calcidiol, 25-hydroxycholecalciferol (abbreviated 25(OH)D3). Ergocalciferol (vitamin D2) is converted in the liver to 25- hydroxyergocalciferol (25(OH)D2). It is widely known that circulating 25(OH)D is the best indicator of vitamin D status.[2,3] 25(OH)D3 is then converted in the kidneys (by the enzyme 25(OH)D-a-hydroxylase) into 1,25-(OH)2D3, a steroid hormone that is the active form of vitamin D. It can also be converted into 24-hydroxycalcidiol in the kidneys via 24-hydroxylation.[4,5] 1,25-(OH)2D3 circulates as a hormone in the blood, regulating the concentration of calcium and phosphate in the bloodstream and promoting the healthy growth and remodeling of bone. 1,25-(OH)2D3 also affects neuromuscular and immune function. Vitamin D has a significant role in calcium homeostasis and metabolism. Its discovery was due to effort to find the dietary substance lacking in rickets (the childhood form of osteomalacia). This test can be used to diagnose vitamin D deficiency, and it is indicated in patients with high risk for vitamin D deficiency and when the results of the test would be used as supporting evidence for beginning aggressive therapies. Patients with osteoporosis, chronic kidney disease, malabsorption, obesity, and some other infections may be high risk and thus have greater indication for this test.[9,10]
- 1.Holick MF (March 2006). "High prevalence of vitamin D inadequacy and implications for health". Mayo Clin. Proc. 81 (3): 353–73.
- 2.Hollis BW (January 1996). "Assessment of vitamin D nutritional and hormonal status: what to measure and how to do it". Calcif. Tissue Int. 58 (1): 4–5.
- 3.Holick MF, Schnoes HK, DeLuca HF, Suda T, Cousins RJ (1971). "Isolation and identification of 1,25-dihydroxycholecalciferol. A metabolite of vitamin D active in intestine". Biochemistry 10 (14): 2799–804.
- 4. Bender, David A.; Mayes, Peter A (2006). "Micronutrients: Vitamins & Minerals". In Victor W. Rodwell; Murray, Robert F.; Harper, Harold W.; Granner, Darryl K.; Mayes, Peter A. Harper's Illustrated Biochemistry. New York: Lange/McGraw-Hill. pp. 492–3.
- 5.Institute of Medicine (1997). "Vitamin D". Dietary References Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, D.C: National Academy Press. p. 254.
- 6."Dietary Supplement Fact Sheet: Vitamin D". Office of Dietary Supplements (ODS). National Institutes of Health (NIH). Retrieved April 11, 2010.
- 7.Wolf G (June 2004). "The discovery of vitamin D: the contribution of Adolf Windaus". J Nutr 134 (6): 1299–302.
- 8.Sattar, N.; Welsh, P.; Panarelli, M.; Forouhi, N. G. (2012). "Increasing requests for vitamin D measurement: Costly, confusing, and without credibility". The Lancet 379 (9811): 95–96.
- 9. Bilinski, K. L.; Boyages, S. C. (2012). "The rising cost of vitamin D testing in Australia: Time to establish guidelines for testing". The Medical Journal of Australia 197 (2): 90.
- 10.Lu, Chuanyi M. (May 2012). "Pathology consultation on vitamin D testing: Clinical indications for 25(OH) vitamin D measurement [Letter to the editor]". American Journal Clinical Pathology (American Society for Clinical Pathology) (137): 831–832.,