The vitamin d hormonal system: implications for bone diseases

A half century ago, vitamin D was recognized as a vitamin. Now it has become clear that it is also a hormone--indeed the biochemical cornerstone of a major hormonal system involved in regulating the body's calcium economy. The active metabolite, calcitriol, produced in the kidney, acts on bone and intestine and has been found effective in therapy of osteodystrophy and perhaps other metabolic bone diseases.