[Active vitamin D and vitamin K as therapeutic agents for osteoporosis].

Active vitamin D has been most widely used in Japan for the treatment of osteoporosis. However, clinical evidence for its efficacy as an anti-osteoporotic drug is scarce in terms of fracture prevention. Recent reports suggest that active vitamin D may prevent fracture not only through enhancement of intestinal calcium absorption but also by improving bone quality and/or strength independently of bone mass and by improving neuromuscular function to reduce the number of fall. Low serum concentrations of vitamin K have been reported in patients with osteoporosis, and serum osteocalcin appears to be undercarboxylated in these individuals, a process dependent on vitamin K. Undercarboxylated osteocalcin is also a significant risk for hip fracture. Clinical studies in Japan suggest that menatetrenone (vitamin K2) reduces skeletal losses and, in a small randomized clinical trial, it reduced the rate of vertebral fractures. Menatetrenone is currently used in Japan, the Republic of Korea and Thailand.