CYP27B1 and hyperinsulinemic hypoglycemia, familial, 4: In our study, Cyp27b1−/− mice showed the long-time status of 1,25(OH)2D3 deficiency while 1,25(OH)2D3 deficient diet indicated the short-time 1,25(OH)2D3 deficiency, which might result in the different effects on gut microbiota.