CYP24A1 and osteogenesis imperfecta type 3: More severely affected patients (type III OI) tended to have lower 25OHD levels, higher serum 24,25(OH)2D levels and a higher serum 24,25(OH)2D to 25OHD ratio, suggesting increased 25OHD 24-hydroxylase (CYP24A1) activity [23].