Bone mineral density after surgical treatment for Graves' disease.

Abstract

Restoration of bone loss associated with thyrotoxicosis follows normalization of thyroid function. However, the extent of bone loss and restoration remain controversial. To clarify whether bone recovery is complete, we examined lumbar and femoral bone mineral density (BMD) by dual-energy x-ray absorptiometry (DXA) in 14 thyrotoxic premenopausal women with Graves' disease and 31 premenopausal women treated for Graves' disease by subtotal thyroidectomy who had been in remission for at least 3 years. In the remission group, to exclude the influence of subclinical hyperthyroidism, thyrotropin (TSH) levels were followed and subjects with low levels excluded. Thus, all 31 subjects had normal thyroid hormone levels with transiently or persistently elevated TSH levels post-thyroidectomy. Data from the two study groups were compared with those from healthy premenopausal controls matched for age, height and weight. Mean lumbar (anterior-posterior and lateral), femoral neck, and trochanter BMDs were significantly lower in the thyrotoxic group than in controls (p < .05, all four BMDs). Mean lumbar (anterior-posterior), femoral neck and trochanter BMDs were significantly higher in the remission group than in controls (p < 0.05, all three BMDs). At the time of DXA, the 31 remission subjects showed a significant positive correlation between lumbar BMD and TSH (p < 0.05) and a significant negative correlation between femoral neck BMD and free triiodothyronine (FT3) (p < 0.05). These observations suggest: (1) in premenopausal women, bone loss associated with thyrotoxicosis due to Graves' disease is present but is fully restored when remission is reached after subtotal thyroidectomy; (2) subclinical hypothyroidism after subtotal thyroidectomy may result in higher BMD than that of controls.