CYP27A1 and X-linked hypophosphatemia: To further understand the potential role of sclerostin in bone metabolism and the serum sclerostin levels in different metabolic diseases, serum sclerostin levels were measured in patients with OI, XLH, and PDB, and the correlation between serum sclerostin levels and β-CrossLaps of type 1 collagen containing cross-linked C-telopeptide (β-CTX) was analyzed.