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To: tom pope who wrote (6681)	11/3/2009 1:59:50 PM
From: Biotech Jim	Read Replies (1) \| Respond to of 7143

Tom- All three of the tests should be used if one wants the entire picture. Vit D is the parent, but 2 metabolic transformations have to take place for full activity. The liver has the 25 hydroxylase enzyme that puts a hydroxyl on the 25 position. then, this 25-hydroxy Vit D goes via the blood stream to the kidney where the 1 alpha hydroxylase resides. This enzyme then makes the product 1,25-dihydroxy Vit D, which is the most biologically active form of Vit D in terms of its calcium-related activities. If you want only 1 test, use either the Vit D or the 1,25-dihydroxy Vit D test. I used to work with Hector DeLuca in the University of WIsconsin Biochemistry department where a lot of this work was discovered. Quite an exciting time back then, and thanks to the National Science Foundation that I received the summer undergraduate fellowship. BTW, Mike Hollick was at that time finishing up his PhD work with Hector, and today Mike is one of the key clinicians studying Vit D. BJ

To: tom pope who wrote (6681)	11/3/2009 2:42:08 PM
From: Ian@SI	Read Replies (3) \| Respond to of 7143

Tom, The Vitamin D, 25-Hydroxy at $59.99 is the measurement that I see most often cited in Research abstracts. Anything below 30ng/ml or 75 nmol/l would be viewed as insufficient or deficient by most researchers. Top end of the "normal" range is about 300 nmol/l. I think that the highest natural level is about 60-70ng/ml (150-175nmol/l). But I've only seen this number once and don't have a high level of confidence in its accuracy. While Biotech Jim's response is far more definitive, getting a single test is probably an appropriate starting point, at least until you find out whether or not there's an issue. FWIW, Ian