The effect of total thyroidectomy on the recovery of bone mineral density in subjects with hyperthyroidism.

Background: Although hyperthyroidism is associated with high turnover osteopenia and its recovery after treatment, the extent of recovery with different forms of therapy remains controversial. This prospective study evaluated the bone mineral density in thyrotoxic subjects undergoing total thyroidectomy and I radioactive iodine therapy.

Methods: Newly diagnosed subjects with hyperthyroidism undergoing total thyroidectomy (group 1; n = 127) and I radioactive iodine therapy (group 2; n = 30) were evaluated for bone mineral density by dual energy x-ray absorptiometry at the time of diagnosis (point A), on achieving euthyroidism with antithyroid drugs (point B), and 6 months after definitive treatment (point C).

Results: In group 1, bone mineral density (expressed as g/sq cm; mean ± standard deviation) in the hip (0.842 ± 0.157) and spine (0.97 ± 0.155) at point A, improved at point B (hip, 0.853 ± 0.157 and spine, 0.982 ± 0.155), and further improved at point C (hip, 0.91 ± 0.158 and spine, 1.053 ± 0.161, each P < .001). In group 2, at point C, bone mineral density in the hip (0.761 ± 0.168 versus point A, 0.741 ± 0.146) and spine (0.831 ± 0.159 versus point A, 0.823 ± 0.158) were less than group 1 (each P < .01).

Conclusion: Bone mineral density improved significantly after all forms of treatment of hyperthyroidism and was greatest in lumbar vertebrae (8.6%) as early as 6 months after total thyroidectomy. The delayed recovery of bone mineral density after I radioactive iodine therapy needs long-term evaluation.