Pathogenesis of Thalassemia Major-associated Osteoporosis: A Review with Insights from Clinical Experience

Abstract

Due to increasing life expectancy in thalassemia major (TM), osteoporosis is emerging as a significant problem. Its aetiology is multifactorial, culminating in increased bone resorption and impaired remodelling. Hypogonadism and marrow expansion seem to play an important role, but iron overload, deferoxamine toxicity, a defective growth hormone-insulin-like growth factor-1 axis and multiple endocrinopathies may represent additional causes of bone damage. Many of these patients, though under appropriate treatment programs, do not achieve normal peak bone mass. The receptor activator of nuclear factor kappa-ß (RANK)/RANK ligand/osteoprotegerin and the Wnt/β-catenin systems work as major mediators of imbalanced bone turnover and bone loss. Additional genetic factors, such as collagen type 1 alpha 1 and vitamin D receptor gene polymorphisms, may exert some influence on the enhanced fracture risk observed in TM. To date, in spite of adequate hormone replacement, chelating therapy and acceptable haemoglobin levels, subjects with TM display impaired bone density and imbalanced bone turnover, thus the puzzle of the pathogenesis of TM-induced osteoporosis remains far from being solved.

Keywords: hypogonadism; thalassemia major; Osteoporosis; marrow expansion; bone turnover.

Figure 1

Pathogenesis of low bone mineral density in thalassemic patients GH-IGF-1: growth hormone-insulin-like growth factor-1

Figure 2

Possible causes for uncoupling bone turnover in thalassemic patients IGF-1: insulin-like growth factor-1, RANKL/OPG: receptor activator of nuclear factor kappa-ß/osteoprotegerin