PHYSIOLOGY AND PATHOLOGY OF VITAMIN D

Excerpt

Vitamin D prevents or cures rickets. Until recently this factor was thought to be a single substance. The active compound formed by the irradiation of ergosterol was considered identical with the antirachitic agents present in natural products or formed in animals or foods by ultraviolet irradiation. It was found, however, that different sources of vitamin D might have different relative values, depending on whether the products were tested with rats or with chickens. It was found also that several different sterols, carefully purified, could be activated by various methods. The multiple nature of vitamin D thus became established, and Bills recently has described ten different substances which are capable of exerting a vitamin D effect. As more information becomes available regarding the chemical nature of the different forms of vitamin D, there may be afforded a clearer understanding of the physiologic and pharmacologic aspects of each active substance. At the