Risk factors and bone mineral density in female patients with long-term treatment with levo-thyroxine

BACKGROUND: It is controversial if the long-term treatment with thyroid hor mone given at substitutive or suppressive doses has a negative effect on bo ne metabolism. In previous reports the lack of ultrasensitive TSH assays an d densitometers with adequate precision, and the heterogeneity of the patie nts analyzed could explain these discordant results. PATIENTS AND METHODS: We have asessed bone mineral density (BMD) in 43 prem enopausal and 53 postmenopausal women, who underwent near total thyroidecto my and I-(131) ablation due to differentiated thyroid cancer, that have bee n followed up (mean duration, 75.5 [43] months) with suppressive thyroid ho rmone treatment (mean dose, 170 [42] mu g) in our hospital. Patients with h istory of hyperthyroidism were excluded. Lumbar BMD (L-2-L-4) and BMD in th ree different sites of hip were measured (dual X-ray densitometry) to deter mine the contribution of several clinical and risk factors associated with thyroid hormone therapy given to BMD. RESULTS: We have not found significant decrease in BMD at spine or hip when patients were compared with healthy, age and sex matched, Age (inverse cor relation) and weight (direct correlation) were the variables mostly influen cing BMD). Histologic type of thyroid neoplasia, doses of thyroid hormones, thyroid hormone levels and duration of follow-up, were not associated with changes in BMD. A decrease in calcium intake in postmenopausal and less ph ysical activity in premenopausal women were related with a decreased lumbar BMD. CONCLUSIONS: During long-term treatment of female patients with thyroid hor mones, other risk factors should be studied in order to prevent possible lo ss of hone mass.