[Bone density in differentiated cancer of the thyroid gland treated by hormone-suppressive therapy. Study based on 51 cases].

The effect of L-Thyroxine suppressive therapy (207.3 +/- 46.1 mcg/d) on lumbar spine bone density (BMD) was assessed in 51 patients thyroidectomized for carcinoma since 1 to 19 years (mean = 6 +/- 5.4 years); the bone densities of these patients were compared with those of 51 age sex weight-matched control subjects. Trabecular bone density was evaluated by single energy quantitative tomography. The vertebral BMD was not significantly different between the patients receiving suppressive doses of L-T4 and the control group (162.8 +/- 40.4 vs 162.7 +/- 39.8 mg/cm3). We found no relationship between the duration of L-Thyroxine therapy and BMD. Thus, doses of L-T4 sufficient for suppressing plasma thyroid stimulating hormone but no high enough for causing biochemical thyrotoxicosis have no harmful effect on trabecular bone mineral density.