Normal range of vitamin D: relationship between serum PTH and bone mineral density

To quantify the relationship between serum PTH, vitamin D and bone mineral density to determine normal range of vitamin D in normal population.

A total of 830 healthy individuals aged 30 to 76 years old (60.8% women, 39.2% men) living in Tehran were randomly selected, following exclusion of people suffering from endocrine, rheumatologic or chronic diseases, fractures, other conditions or using drugs that affecting bone metabolism. Vitamin D and Ca intakes were assessed with a food frequency questionnaire. Self-reported daily time of sun exposure was used to categorize exposure to sunshine. All participants underwent clinical examination and lumbar spine and proximal of femur BMD by using dual-energy X-ray absorptiometry technique. Plasma level of 25(0H) D, Ca, Phosphate (P), Alkaline phosphatase (ALK P), parathyroid hormone {PTH) measured during winter. The correlation between these results was investigated.

PTH correlated inversely with 25(0H) D .In multivariate analysis PTH correlated inversely with whole body BMD (mostly lumbar spine) but not with the hip BMD. No association was found between 25(0H) D levels and BMD at any site in univariate or multivariate analysis. Based on this relationship between PTH, vitamin D and BMD we obtained normal range of vitamin D. Cut -off point for sever vitamin D deficiency was lower than l 8nmol/l and range of moderate & mild were I 8-23 & 23-36 nmol/1, respectively.

Normal range determination of vitamin D based on relationship between PTH, vitan..n D and BMD can be shown biological bone variation and is useful in prevention strategy.