BONE-MINERAL DENSITY AFTER SURGICAL-TREATMENT FOR GRAVES-DISEASE

Restoration of bone loss associated with thyrotoxicosis follows normal ization of thyroid function. However, the extent of bone loss and rest oration remain controversial. To clarify whether bone recovery is comp lete, we examined lumbar and femoral bone mineral density (BMD) by dua l-energy x-ray absorptiometry (DXA) in 14 thyrotoxic premenopausal wom en with Graves' disease and 31 premenopausal women treated for Graves' disease by subtotal thyroidectomy who had been in remission for at le ast 3 years. In the remission group, to exclude the influence of subcl inical hyperthyroidism, thyrotropin (TSH) levels were followed and sub jects with low levels excluded. Thus, all 31 subjects had normal thyro id 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, a nd trochanter BMDs were significantly lower in the thyrotoxic group th an in controls (P < .05, all four BMDs). Mean lumbar (anterior-posteri or), femoral neck and trochanter BMDs were significantly higher in the remission group than in controls (P < 0.05, all three BMDs). At the t ime of DXA, the 31 remission subjects showed a significant positive co rrelation between lumbar BMD and TSH (P < 0.05) and a significant nega tive correlation between femoral neck BMD and free triiodothyronine (F T3) (p < 0.05). These observations suggest: (1) in premenopausal women , bone loss associated with thyrotoxicosis due to Graves' disease is p resent but is fully restored when remission is reached after subtotal thyroidectomy; (2) subclinical hypothyroidism after subtotal thyroidec tomy may result in higher BMD than that of controls.