Vitamin D levels for optimum bone health

Masud F
Correspondence: Dr Faisal Masud, dr.faisalmasud@gmail.com

ABSTRACT
Introduction Vitamin D deficiency was assessed previously on the basis of rickets and osteomalacia, which represent an extreme end of the spectrum. As a result of this, many clinically-asymptomatic patients go undetected. As vitamin D deficiency results in secondary hyperparathyroidism, we propose to use the normalisation of intact parathyroid hormone (iPTH) as a surrogate marker for assessing the adequacy of vitamin D nutrition.
Methods A descriptive study was undertaken on 195 premenopausal Pakistani women. 25-hydroxy-cholecalciferol and iPTH levels were measured by standard laboratory techniques.
Results The minimum level of vitamin D required to keep iPTH below 53 pg/dL was found to be 16 ng/ml with a 95 percent confidence interval of 13.8 and 18.2. Existing normal range is 9-36 ng/ml.
Conclusion Normalisation of iPTH if taken as a criterion for judging vitamin D deficiency can lead to detection of clinically asymptomatic patients. The simplicity, low cost of correction, and the potential beneficial skeletal and non-skeletal consequences of doing so makes it essential that this criterion be used to redefine the optimal vitamin D levels. This should be internationally standardised and made available to clinicians.

Keywords: 25-hydroxy-cholecalciferol, osteomalacia, rickets, secondary hyper-parathyroidism, vitamin D levels
Singapore Med J 2007; 48(3): 207–212