The Effect of TSH Suppression on Vertebral Trabecular Bone Scores in Patients With Differentiated Thyroid Carcinoma.

Context: The effect of thyrotropin (TSH) suppressive therapy on trabecular bone scores (TBSs) is unclear.

Objective: The aim of this study was to investigate the effect of TSH suppression on vertebral TBSs of postmenopausal women with differentiated thyroid carcinoma (DTC).

Design, Setting, And Participants: We conducted a retrospective cohort study including 273 postmenopausal women with DTC who had received TSH suppressive therapy. Bone mineral density (BMD) and TBSs at the lumbar spine were analyzed using dual-energy X-ray absorptiometry (DXA).

Major Outcome Measure: The association between the parameters of TSH suppressive therapy and bone parameters was investigated.

Results: Study subjects showed upper-normal free thyroxine levels and suppressed TSH at DXA evaluation. The mean duration of TSH suppression was 4.4 ± 2.9 years. Serum free T4 and TSH were not independently associated with lumbar spine BMD or TBS levels. Duration of TSH suppression was negatively correlated with lumbar spine TBS levels, but not with BMD. Longer duration of TSH suppression was independently associated with lower lumbar spine TBSs after adjusting for age, body mass index (BMI), and BMD. Lumbar spine TBSs were significantly lower in patients whose duration of TSH suppression was ≥5 years compared with those whose duration was <3 years after adjusting for age, BMI, and BMD.

Conclusions: Longer duration of TSH suppression in postmenopausal DTC patients was associated with decreased vertebral bone strength by altering TBSs rather than BMD. TBSs should be considered when estimating vertebral bone fragility in postmenopausal DTC patients receiving long-term TSH suppressive therapy.