Thyroid-Stimulating Hormone Within Normal Range Does Not Affect Bone Turnover in Euthyroid Postmenopausal Women with Osteoporotic Fracture - A Preliminary Report

BACKGROUND: Pathogenic role of TSH suppression in the damaged bone tissue, in contrast to increased concentrations of thyroid hormones is still unknown. The aim of study was to evaluate the relationship between serum TSH and biochemical bone turnover markers in postmenopausal women with normal thyroid function and to answer whether the differences in TSH concentration within reference range may affect bone metabolism. MATERIAL AND METHODS: 34 women (60-93 years old) admitted to the hospital after osteoporotic fracture participated in the study. Serum propeptide of type 1 procollagen (P1NP) as a bone formation marker and crosslinked C-terminal telopeptides (CTX-I), as a bone resorption marker and TSH were assayed. RESULTS: Median P1NP (p=0,05) was significantly higher in the 1st tertile of TSH values (0,35-1,88 mlU/mL). In the 3rd tertile of TSH concentrations (3,42-4,94 mlU/mL), the highest CTX-I value was found that exceed the reference range for age. No differences were found in bone markers between a group of euthyroid and a group of subjects with TSH<0,35 mlU/mL. No relationship was observed between TSH and bone formation and resorption markers in the whole group of euthyroid postmenopausal women, however bone formation was found to be in the lower reference range for age in the euthyroid subjects as well as in these with decreased TSH. Weight and BMI correlated negatively with CTX (r=-0,68 p<0,03) in fractured women in the 1st tertile of TSH. CONCLUSION: We found no consistent evidence that TSH concentrations within reference range was associated with changes in bone turnover markers.