Receptor Activator of Nuclear Factor κ-Β Ligand/Osteoprotegerin Axis in Adults with Hb S/β-Thalassemia and β-Thalassemia Trait

Abstract

There is not enough data about osteoporosis and the role of receptor activator of nuclear factor κ-Β ligand (RANKL)/serum osteoprotegerin (OPG) system in patients with double heterozygosity for sickle cell disease and β-thalassemia [Hb S (HBB: c.20A>T)/β-thal] and β-thal trait. Aim of the study was to investigate bone mineral densities (BMD) and the role of RANKL/OPG system in these cases. We studied 58 adults with Hb S/β-thal, 52 adults with β-thal trait, 34 healthy subjects as a control group. The BMD was determined by dual-energy X-ray absorptiometry (DEXA). Biochemical markers of bone metabolism (serum calcium, phosphorus, alkaline phosphatase, osteocalcin) parameters that affect bone metabolism (serum parathyroid hormone, thyroid-stimulating hormone, 25-hydroxyvitamin D, OPG, soluble RANKL [sRANKL]) were studied. Femoral neck Z-scores of 93.2% for β-thal trait, 83.0% for Hb S/β-thal patients were within the expected range. Lumbar spine Z-scores of 89.1% for β-thal, 90.2% for Hb S/β-thal patients were above −2.0 SD. Z-scores of the control group were within the expected range. Median serum sRANKL level was 2.80, 4.52, 5.79 pmol/L in Hb S/β-thal, β-thal trait, control groups, respectively (p = 0.010). Median serum OPG level was 1.07, 0.86, 0.86 pmol/L in Hb S/β-thal, β-thal trait, control groups, respectively (p < 0.001). β-Thalassemia trait alone is not a risk factor for osteopenia/osteoporosis and osteoporosis does not develop in premenopausal women and men younger than 50 years with Hb S/β-thal. However, as we determined lower levels of osteocalcin, compensatory decrease of sRANKL with compensatory increase of OPG, more severe osteoporosis may develop in advanced ages in these patient populations.