Abstract
Context:Sclerostin inhibits bone formation and is involved in the bone response to mechanical loading, but the role and significance of circulating sclerostin is poorly understood.
Objective:We assessed the association between serum sclerostin and calcitropic hormones, bone turnover marker levels, bone mineral content/density (BMC/BMD), and microstructure using three different immunoassays.
Design, Setting, and Participants:In a cross-sectional study, serum sclerostin was measured in a cohort of 187 healthy subjects (98 women; 89 men) aged 65±1 (x±SD) years.
Results:Overall, mean sclerostin (95% CI) was 37.3 (18.0-69.2) ng/l, 1165.8 (464.0-2296.4) ng/l, and 513.5 (250.7-950.9) ng/l with assays I, II and III, respectively. Serum sclerostin was higher in men with assays II and III. In all three assays, sclerostin and PTH were inversely correlated, only after adjustment for whole-body BMC (WB-BMC). After adjustment for sex and WB-BMC, the bone turnover markers P1NP and CTX negatively correlated, only with assay II. In all three assays, sclerostin positively correlated to WB-BMC, distal radius and distal tibia cortical area, cancellous bone volume (BV/TV) and trabecular number, and lumbar spine and proximal femur areal BMD following adjustment for sex.
Conclusion:Sclerostin levels are markedly different according to the immunoassay used. Detection of an association with calcitropic hormones or turnover markers relies on the epitope recognized by the immunoassay and adjustment for bone mass.