Abstract
In vitamin D research, there are three milestones from the perspective of pharmaceutical studies. The first represents the early stage of vitamin D research and involves the discovery of vitamin D and its physiological significance as an anti-rickets factor. The second is the elucidation of the vitamin D activation pathway in the body and the discovery of the biologically active metabolites of vitamin D. The clinical application of active vitamin D or its prodrug was also attempted to make up for the deficiency caused by poor vitamin D activation. The third is characterized by the discovery of the differentiation-inducing properties of active vitamin D. This showed the diversity of the physiological actions of active vitamin D, which initially had been thought only to contribute to bone and calcium metabolism. Because these physiological actions were clinically useful, the third discovery revealed opportunities for the development of drugs appropriate to specific purposes by synthesizing analogs to separate biological effects. Active vitamin D analogs based on the findings during the third milestone are now commercially available and are contributing to current clinical practice. This article discusses the various milestones outlining vitamin D and analogs in terms of clinical applications and pharmaceutical studies.
