Relationship between serum thyroid stimulating hormone levels and serum osteoprotegerin levels and bone mineral density in healthy men / 대한내과학회지

ABSTRACT

BACKGROUND: In untreated hyper or hypothyroidism decreased bone mineral density (BMD) has been demonstrated. Studies on fracture risk in patients with hyper or hypothyroidism have reported an increased risk of osteoporotic fractures. The osteoporosis associated with thyroid dysfunction is traditionally viewed as a secondary consequence of altered thyroid function. Recently, there was a report about direct effects of thyroid stimulating hormone (TSH) on both components of skeletal remodeling, osteoblastic bone formation, and osteoclastic bone resorption, mediated via the TSH receptor found on osteoblast and osteoclast precursors. Thus, the aim of this study was to investigate the relationship between serum TSH levels, and osteoprotegerin (OPG)/ receptor activator of NF-B ligand (RANKL) system and bone mineral density in healthy men with euthyroid function. METHODS: We observed 75 korean men (mean age, 54.5 yr) with euthyroid function. Serum concentrations of TSH, free thyroxine, total testosterone, estradiol, insulin-like growth factor I (IGF-I) and biochemical markers of bone turnover were measured by standard methods. Enzyme-linked immunosorbent assay determined serum concentrations of OPG and RANKL. BMD at lumbar spine and femoral neck were measured by dual energy X-ray absorptiometry. RESULTS: When the BMD at lumbar spine or femoral neck were examined as the dependent variable in multiple regression analysis, serum total testosterone, estradiol and IGF-I levels were identified as a significant predictor for BMD at lumbar spine, and only serum IGF-I levels for BMD at femoral neck. For Serum OPG or RANKL levels as the dependent variable, serum TSH, estradiol levels and BMD at femoral neck were identified as a significant predictor for serum OPG levels, and only serum estradiol levels for serum RANKL levels. CONCLUSION: Our data shows that the serum TSH levels are independently associated with serum OPG levels in healthy men with euthyroid function, but not associated with BMD. Our observations suggest that serum TSH levels are partly related with resorptive mechanism of bone metabolism in men, but further research is needed to establish its relation with TNF and other pro-resorptive cytokines.