Endocrine Abstracts

Introduction: Sclerostin is well-known as an inhibitor of bone formation but also promotes bone resorption. Acromegaly is a disease characterized by increased bone turnover and higher vertebral fracture risk.

Purpose: The aim of the study was to determine sclerostin levels in acromegaly patients with regard to the disease activity. We also evaluated the associations between sclerostin and random growth hormone (GH), insulin-like growth factor 1 (IGF-I), lumbar spine (LS) bone mineral density (BMD), femoral neck (FN) BMD and fracture risk.

Material and methods: A study group consisted of 72 patients with acromegaly, and was divided into three subgroups: active acromegaly (AA), controlled acromegaly (CTA) and cured acromegaly (CA). Fifty-four age- and sex-matched subjects were enrolled to the control group (CG). Blood samples were obtained from all participants to assess sclerostin, GH, IGF-I. The patients were questioned about clinical risk factors of fracture. Dual-energy x-ray absorptiometry was performed at two sites: LS and hip. Further, we estimated the ten-year probability (10yp) of major osteoporotic and hip fractures using FRAX calculator online.

Results: The patients with acromegaly had significantly lower sclerostin levels than CG, despite of subject classification (AA vs CG; CTA vs CG; CA vs CG; AA+CTA+CA vs CG; CTA+CA vs CG; P<0.05). Significantly higher probability of major osteoporotic and hip fractures was observed in the following groups: AA+CTA+CA, CTA+CA, CTA compared with CG. There were no significant differences in sclerostin levels among the subgroups of patients with acromegaly. Sclerostin correlated positively with the 10yp of major osteoporotic fracture in the groups: AA+CTA+CA (P=0.003), CTA+CA (P=0.013) and with the 10 yp of hip fracture in the groups AA+CTA+CA (P=0.001), CTA+CA (P=0.001) and CTA (P=0.007). No significant correlations were found between sclerostin levels and GH, IGF-I, LS BMD and FN BMD.

Conclusion: Acromegaly is associated with higher fracture risk. Lower sclerostin levels in patients with acromegaly may reflect a compensatory mechanism to increased bone turnover.