Variable bone mass recovery in hyperthyroid bone disease after radioiodinetherapy in postmenopausal patients

Objectives: Long-term follow-up of postmenopausal hyperthyroid females afte r radioiodine therapy, since hyperthyroidism is known to cause impressive b one loss which may increase the risk of bone fractures. Methods: Bone miner al density (BMD) and biochemical parameters of bone metabolism in hyperthyr oid postmenopausal patients were investigated before and 2 years after radi oiodine therapy and compared with euthyroid age-matched controls. Results: At baseline, the incidence of low BMD with t-scores more than 2.5 S.D. belo w normal was significantly higher in hyperthyroid patients (54%) than in co ntrols (20%. P < 0.001). Regardless of initial BMD values, osteocalcin (OC) was also higher in all hyperthyroid patients (P < 0.0001). After 2 years, all treated patients were euthyroid and OC levels were in the upper normal range. In hyperthyroid patients with initially low BMD, bone density values had increased significantly by + 6.5% (P < 0.008) as compared with baselin e values. In contrast, hyperthyroid patients with initially normal BMD show ed a further decrease in lumbar BMD values of -4.3% despite radioiodine tre atment. BMD in euthyroid controls decreased by -6.5% within 2 years. Conclu sions: We conclude that hyperthyroid postmenopausal patients with generally increased bone turnover may show individual differences in bone loss and B MD recovery after radioiodine treatment. The mechanisms for this variable m anifestation of osteoporosis have still to be elucidated, since this has im plications for prophylactic and therapeutic strategies in these elderly pat ients. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.