Low Level of Serum Sclerostin in Adult Patients with Tumor-induced Osteomalacia Comparing with X-linked Hypophosphatemia.

Context Sclerostin is an inhibitor of Wnt-β-catenin signaling to regulate bone formation. Circulating sclerostin levels were reported to be elevated in patients with X-linked hypophosphatemia (XLH), and sclerostin antibody (Scl-Ab) has been shown to increase bone mass and normalize circulating phosphate levels in Hyp mice. However, circulating sclerostin level in acquired hypophosphatemic patients with tumor-induced osteomalacia (TIO) remains rare reported. Objectives This study was designed to evaluate serum sclerostin levels in TIO patients comparing them with age-, sex- matched healthy controls and XLH patients, and analyze correlation of circulating sclerostin with BMD and laboratory parameters. Design, setting and participants 190 individuals including 83 adult TIO patients, 83 adult healthy controls and 24 adult XLH patients were enrolled in this cross-sectional study. Main outcome measures Serum sclerostin levels were determined in TIO patients, healthy controls and XLH patients. Results TIO patients (43 male and 40 female) aged 44.3 ± 8.7 (mean ± SD) years had lower levels of circulating sclerostin than healthy controls (94.2 ± 45.8 vs 108.4 ± 42.3 pg/mL, p = 0.01) with adjustment for age, gender, BMI and diabetes rate. Sclerostin levels were positively associated with age (r = 0.238, p = 0.030). Male patients had higher sclerostin level than female patients (104.7 ± 47.3 vs 83.0 ± 41.8 pg/mL, p = 0.014) and postmenopausal patients had higher tendency of sclerostin level than premenopausal patients (98.4 ± 48.8 vs 71.6 ± 32.3 ng/ml, p = 0.05). Sclerostin levels were positively associated with BMD of L1-4 (r = 0.255, p = 0.028), femoral neck (r = 0.242, p = 0.039) and serum calcium (r = 0.231, p = 0.043). TIO subgroup patients (n=24, 35.9 ± 7.3 years old) comparing with age-, sex-matched adult XLH patients and healthy controls revealed significant difference of sclerostin levels (XLH, TIO and healthy control were 132.0 ± 68.8, 68.4 ± 31.3 and 98.6 ± 41.1 pg/mL, respectively, p Conclusions Circulating sclerostin levels were decreased in TIO patients but increased in XLH patients, which might be result of histological abnormality and bone mass.