FGF23 and hypophosphatemia: In conclusion, our study demonstrated significantly lower vBMDs, severely impaired bone microarchitecture, and profoundly weaker bone strength in Chinese adolescent patients with TIR/O, notably at the distal tibia, compared with the same parameters in age- and gender-matched healthy controls and XLH patients, which was possibly caused by excessive FGF23 production and secretion, chronic severe hypophosphatemia, and the lack of a mechanical stimulus at the lower extremities.