Women with Turner syndrome face a high risk of fractures because their bone mineral density is often low. For years it was assumed that hypogonadism — the lack of oestrogen caused by ovarian failure — was the main factor. But whether other lifestyle elements, such as diet or exercise, contributed to the deficit remained unclear. A Japanese multicentre prospective observational study, coordinated by Osaka Children’s Hospital and Kanagawa University Medical Centre, has now assessed the role of diet, physical activity and bone turnover markers in 48 patients with Turner syndrome aged 5 to 49.
The cohort was divided into three groups: nine prepubertal patients, six with cyclical menstruation and 33 on hormone replacement therapy. The latter two were grouped together as the postpubertal group. Vertebral bone mineral apparent density was expressed as a Z-score, which compares each patient’s value with that of people of the same age and sex. The result showed a clear difference between stages: mean Z-score was -0.3 standard deviations in the prepubertal group and -1.8 in the postpubertal group, a statistically significant difference.
Within the postpubertal group the most relevant finding appeared. The six participants who maintained cyclical menstruation had a median Z-score of -0.2 standard deviations, while the 33 receiving hormone replacement therapy had -2.3. The difference was significant. That is, patients with residual ovarian function retained much better bone, reinforcing the idea that endogenous oestrogen, more than any other factor, protects bone mass. The authors found no correlation between the Z-score and bone metabolism markers, nor any significant relationship with vitamin D sufficiency or the number of daily steps recorded.
They did observe negative correlations: between bone density and serum sclerostin in the prepubertal group, and between bone density and follicle-stimulating hormone (FSH) in the postpubertal group. Sclerostin is a protein that restrains bone formation, and a high FSH signals advanced ovarian failure. Both links point in the same direction. The study concludes that diet and exercise habits did not explain the differences in bone density in these patients and that oestrogen deficiency is the chief reason for the problem. For clinical practice, this underlines the importance of getting hormone replacement therapy right, rather than placing on lifestyle changes a responsibility that hormonal biology explains better.
Source: Factors associated with low bone mineral density in Turner syndrome: a multicenter prospective observational study. Ikegawa K, Koga E, Itonaga T, Sakakibara H, Kawai M, Hasegawa Y. Endocrine Journal 2024;71(6):561-569. DOI: 10.1507/endocrj.ej23-0628.
