Serum 25-Hydroxyvitamin D Concentrations and Risk for Hip Fractures

Cauley JA, et al. (2008). Ann Intern Med 149(4):242-50

Women with the lowest 25(OH) vitamin D concentrations (47.5 nmol/L) had a higher fracture risk than did those with the highest concentrations (70.7 nmol/L) (adjusted odds ratio, 1.71 [CI, 1.05 to 2.79]), and the risk increased statistically significantly across quartiles of serum 25(OH) vitamin D concentration (P for trend = 0.016). This association was independent of number of falls, physical function, frailty, renal function, and sex-steroid hormone levels and seemed to be partially mediated by bone resorption. Low serum 25(OH) vitamin D concentrations are associated with a higher risk for hip fracture.

Overview of general physiologic features and functions of vitamin D

DeLuca HF. (2004) Am J Clin Nutr, 80(suppl):1689S-96S.
Vitamin D3 is a prohormone produced in skin through ultraviolet irradiation of 7-dehydrocholesterol. It is biologically inert and must be metabolized to 25-hydroxyvitamin D3 in the liver and then to 1,25-dihydroxyvitamin D3 in the kidney before function. The hormonal form of vitamin D3, ie, 1,25-dihydroxyvitamin D3, acts through a nuclear receptor to carry out its many functions, including calcium absorption, phosphate absorption in the intestine, calcium mobilization in bone, and calcium reabsorption in the kidney. It also has several noncalcemic functions in the body. This overview provides a brief description of the physiologic, endocrinologic, and molecular biologic characteristics of vitamin D. It also provides information on new selective analogs of 1,25-dihydroyvitamin D3 for therapy.