CYP2R1 and obesity due to melanocortin 4 receptor deficiency: Indeed, vitamin D is a fat-soluble steroid hormone and itsvolumetric dilution into adipose tissue mass when increased is recognized asone of the most plausible explanations for the relationship between vitaminD deficiency and obesity (56,57).Experimental studies suggest that obesity is associated with decreasedexpression of specific genes that regulate the metabolism of vitamin D byaltering synthesis of the enzymes CYP2R1 and CYP27B1 (58).