Background and aim: Subjects with Turner Syndrome (TS) show low cortical bone mineral density (BMD), osteoporosis and risk of fractures. Previously, we demonstrated the enhanced spontaneous osteoclastogenesis in girls and young women with TS before and after pubertal induction with hormonal replacement therapy (HRT). The bone resorption observed in girls before puberty induction seems to be supported by the high FSH serum levels observed at prepubertal stage, while in young women on continuous HRT the effects on osteoclasts seem to be mediated mostly by high RANKL levels. We aimed to investigate if osteoblast differentiation/activity could also be impaired in girls with TS.
Method: Markers of bone remodelling were measured in sera of 10 girls with TS (median age 5.2±1.2) and 10 age matched controls. Bone mineral density was evaluated by DEXA. The percentage of circulating osteoblast precursors CD34+/CD45-/Osteocalcin (OCN)+ cells was evaluated by flow cytometry.
Results: Lumbar spine BMD-Z-score was reduced in 50% TS patients, together with levels of 25-OH Vitamin D. In sera of TS patients we also detected a significant slight increase of the levels of the osteoblastogenesis inhibitor sclerostin compared with the controls (28.45±9.43 vs 20.99±9.31, P<0.01 respectively). Consistently, we also detected a significant low percentage of circulating osteoblast precursors CD34+/CD45-/Osteocalcin (OCN)+ cells in TS patients with respect to the controls (1.1±. 0.2 vs 3.5±0.5 P<0.01, respectively). The percentage of circulating osteoblast precursors positively correlated with the reduced lumbar spine BMD-Z-score (r=0.42, P<0.01) and with the low levels of 25-OH Vitamin D (r=0.45, P<0.01).
Conclusions: In TS patients the low percentage of circulating osteoblast precursors CD34+/CD45-/Osteocalcin (OCN)+ cells together with the high levels of sclerostin sustain the involvement of osteoblasts in the impaired bone remodeling associated to TS.
27 - 29 Sep 2018
European Society for Paediatric Endocrinology