The role of vitamin D in osteoporosis.

It is known that circulating vitamin D predominantly originates from cutaneous synthesis and therefore should be considered as a hormone rather than a vitamin. Vitamin D deficiency (<50nmol/L) is a worldwide epidemic with multiple implications on human health, due to its role in various physiological systems. Various studies have shown that with higher serum 25 hydroxyvitamin D levels, there is a decrease in the incidence of non-vertebral and hip fractures. There is limited research data on the management of vitamin D deficiency using therapeutic doses. The majority of studies focus on lower physiological doses rather than high pharmacological doses. In order to reach serum levels of 75nmol/L from a deficiency state, higher doses than 800-1000IU/day are required. Future focus should be on the implications of a rise in systemic 25(OH)D3 levels from a deficiency state to 75nmol/L on bone density and fracture risk, and the use of high doses in cases of vitamin D deficiency. Vitamin D treatment and supplementation need to be re-evaluated in the light of new evidence suggesting that high pharmacological doses need to be used in order to obtain the desired effect in the prevention of osteoporosis and recurrence of osteoporotic fractures.