IVitamin D yivithamini kwaye ikwayihomoni ye-steroid, ikakhulu kubandakanya i-VD2 kunye ne-VD3, eyakhiwayo ifana kakhulu. IVitamin D3 kwaye i-D2 iguqulwe ibe yi-25 hydroxyl vithamin d (kubandakanya i-25-Dihydroxyl vithamin D3 kunye d2). 25- (oh) i-VD emzimbeni womntu, ukwakhiwa kwezinzile, uxinzelelo oluphezulu. 25- (oh) I-VD ibonakalisa inani lilonke leVitamin D, kunye ne-VION D, ukuze i-25- (o) i-VD ithathwa njengeyona nto ibalulekileyo yokuvavanya inqanaba leVitamin D.Iik I-ImmunocCology kwaye inokunika isiphumo ngaphakathi kwemizuzu eli-15.