Clinical uses for calciotropic hormones 1,25-dihydroxyvitamin D-3 and parathyroid hormone-related peptide in dermatology: A new perspective

The skin is not only the organ for the photosynthesis of vitamin D-3, but also a target tissue for its activated form 1,25-dihydroxyvitamin D-3 (1,25(OH)(2)D-3). Vitamin D-3 is absolutely essential for the development and maintenance of a healthy skeleton. Without an adequate source of vitamin D-3 children develop rickets and the elderly develop osteomalacia and exacerbation of osteoporosis. 1,25(OH)(2)D-3 is a potent inhibitor of proliferation of epidermal cells and, with its analogs, it has been developed for the successful treatment of psoriasis. Not all psoriasis patients, however, respond to 1,25(OH)(2)D-3 and its analogs, Evidence suggests that there may be a defect in the regulation of levels of mRNA for the vitamin D receptor in patients who have partial or no response to 1,25(OH)(2)D-3 therapy, The degree of responsiveness to 1,25(OH)(2)D-3 therapy may also be related to the allelic variations in the vitamin D receptor gene, Parathyroid hormone-related peptide is synthesized by the epidermis and is an endogenous antiproliferative factor, Parathyroid hormone-related peptide agonists and 1,25(OH)(2)D-3 inhibit in vitro and in vivo epidermal proliferation, whereas parathyroid hormone-related peptide antagonists stimulate both epidermal proliferation and hair growth in vivo. Therefore, the calciotropic hormones 1,25(OH)(2)D-3 and parathyroid hormone-related peptide have wide-ranging clinical applications in dermatology.