Suppressive levothyroxine therapy has no significant influence on bone degradation in women with thyroid carcinoma: A comparison with other disordersaffecting bone metabolism

The aim of this study was to examine different influences on bone degradati on (estrogen status, thyroid function, parathyroid function, bone metastase s) with special interest focusing on the significance of suppressive levoth yroxine therapy (LT4) on bone degradation in patients with differentiated t hyroid carcinoma (DTC). Two markers of bone degradation (ELItest NTx = U-NT x; Serum CrossLaps = S-CTx) were used (1) to quantify the influence of diff erent metabolic influences on bone degradation and (2) to compare these two markers with each other. One hundred forty samples of 98 female patients a ges 23-86 years were analyzed. The correlation between the two assays of bo ne degradation was high (r = 0.825; p < 0.001). Both assays demonstrated th at estrogen deficiency, hyperparathyroidism, and bone metastases caused sig nificant increases of bone degradation. A suppressive LT4 therapy, as used for patients with DTC, led to no significant increases of S-CTx and U-NTx. The study indicates that a well-controlled suppressive LT4 therapy has only a minor effect on the degree of bone degradation and that a possible estro gen deficiency in patients with DTC has a greater impact on bone degradatio n. Thus, female patients with DTC on suppressive LT4 therapy and estrogen d eficiency may benefit from hormone replacement therapy, as patients with DT C and normal estrogen levels presented similar results to euthyroid control s.