1α,25-Dihydroxyvitamin D₃ - Not just a calciotropic hormone

1α,25-Dihydroxyvitamin D₃, the hormonal form of vitamin D₃, is widely appreciated to play a central role in calcium and phosphorous homeostasis. It is becoming increasingly clear, however, that the sterol also plays an important role in the regulation of cellular growth, central nervous system function, and immune responsiveness. In this review, I will highlight some of the mechanisms by which 1α,25-dihydroxyvitamin D₃ regulates cellular growth, alters central nervous system function, and immune function.