Furthermore, we show that a 50% relative reduction in total C‐P4H activity and concomitant reduction in 4Hyp coupled with reduced collagen amount in the P4ha1+/−; P4ha2−/− mouse model results in a significant loss of bone mass and strength in the long bones and that the osteopenia is more evident in the proximal tibia, whereas the femoral neck is the weakest site on three‐point bending. This evidence concerns the gene P4HA1 and Osteopenia.