[Requirement of 25-hydroxyvitamin D in prevention of osteoporosis based on a pathophysiological perspective].

Vitamin D insufficiency is one of the risk factors of osteoporosis. Secondary hyperparathyroidism induced by low serum concentration of 25-hydroxyvitamin D (25-D), which is a most important nutritional marker to evaluate vitamin D status, results in bone loss and increase of fracture risk. In this topic, the recent findings related to the circulating concentration of 25-D for the prevention of osteoporosis are reviewed.