VDR and alopecia: Vdr−/− mice develop alopecia, similar to humans with VDDR2A.(8) This is in contrast to 1α(OH)ase−/−mice, or patients with VDDR1A.(3, 4) Thus, studies in Vdr−/− mice demonstrated that VDR actions independent of the 1,25(OH)2D ligand are required for cyclical regeneration of the hair follicle and for cutaneous homeostasis.(48)