Osteoprotegerin and RANKL in the pathogenesis of osteoporosis in patients with thalassaemia major

Abstract

Osteoporosis represents an important cause of morbidity in thalassaemia major patients; the etiopathogenesis is multifactorial and includes expansion of the bone marrow, endocrine disorders, iron overload and genetic factors. Two cytokines, osteoprotegerin (OPG) and receptor activator of nuclear factor kappa B ligand (RANKL), have recently been identified as important mediators in the pathogenesis of osteoporosis. In this study, the possible role of the OPG-RANKL system in the pathogenesis of osteoporosis in thalassemia major is assessed, as well as any correlations between the serum levels of OPG and RANKL and bone mineral density (BMD), 17 beta-estradiol and free testosterone and the relationship between T-score of BMD and OPG/RANKL ratio. In 31 thalassaemia major patients and a control group, the serum values of OPG and RANKL were assayed and correlated with BMD, as well as with the sex hormones values. All the thalassemic patients had reduced BMD and 35.5% presented osteoporosis. The thalassemic patients had significantly higher serum levels of OPG than the controls, while their higher RANKL levels, were at the threshold of significance. The OPG/RANKL ratio showed higher level respect to the controls. No statistically significant correlation was observed between the T-score and RANKL neither between the T-score and OPG nor between T-score and OPG/RANKL ratio. Instead, a statistically significant correlation was found between the T-score and free testosterone and between the T-score and 17 beta-estradiol. There was no correlation between the sex hormones and OPG and RANKL. The increased OPG values in thalassemic patients could be considered to compensate the increased bone turnover. The authors confirm hypogonadism as a primary etiopathogenetic factor in the reduced BMD observed in thalassaemia major patients.