Currently, there is considerable clinical and academic interest in vitamin D as a consequence of a number of developments over the past decade. This was initially related to a recognised resurgence of symptomatic vitamin D deficiency in children in the UK and other countries.

The potential importance of maternal vitamin D status on bone mass in early childhood and the effect of vitamin D supplementation on peak bone mass has been the subject of much research. An additional development has been the recognition that vitamin D may have a physiological extraskeletal role. This aspect has influenced the definition of vitamin D deficiency, and what level should be regarded as optimal.

The recognition of the prevalence of vitamin D deficiency and insufficiency has led to debate as to whether and how we should be treating asymptomatic individuals.

This review consists of two parts, the first focuses on the skeletal aspects of vitamin D, while the second will review some of the potential extraskeletal aspects, the definition of vitamin D deficiency, and our thoughts on indications for measurement and treatment.