The vitamin D endocrine system is critical for the proper development and maintenance of mineral ion homeostasis and skeletal integrity. Beyond these classical roles, recent evidence suggests that the bioactive metabolite of vitamin D, 1,25-dihydroxyvitamin D₃, functions in diverse physiological processes, such as hair follicle cycling, blood pressure regulation, and mammary gland development. This minireview explores the current progress in unraveling the complexities of the vitamin D endocrine system by focusing on four main areas of research: the resolution of the vitamin D receptor crystal structure, the molecular details of 1,25-dihydroxyvitamin D₃-mediated transcription, murine knockout models of key genes in the endocrine system, and alternative vitamin D receptors and ligands.