Decreased bone mineral density in patients with prolonged thyrotoxicosis before and after treatment.

To investigate the effects of prolonged thyrotoxicosis, we measured the bone mineral densities (BMD) of 24 untreated patients who had suffered from symptoms of thyrotoxicosis for at least 1 year. We also recruited 116 healthy Chinese women residing in the Taipei area as normal controls. The BMDs of these 24 patients for the whole body skeleton, lumbar spine, femoral neck, greater trochanter and Ward's triangle were all significantly lower than those of normal controls (one sample t-test, two-tailed alternative). Older patients had lower absolute values and a trend towards more severe bone loss, which was most significant at the femoral trochanter and Ward's triangle (p less than or equal to 0.05). The decrease in BMD was more pronounced in the vertebral bodies than in the proximal femur for all patients, implying predominantly trabecular bone loss in this disease. The BMDs of 10 patients were reevaluated 1 year after successful medical treatment. These 10 patients had remained euthyroid for 1 year with antithyroid drugs and showed a small, but significant, improvement in their BMDs at the lumbar spine and the proximal femur on reevaluation. However, the recovery was far from complete. Our findings suggest that thyrotoxicosis causes a remarkable loss of bone mineral, which cannot be compensated for after 1 year of successful treatment. Thus, early diagnosis and therapeutic intervention are important for preventing osteoporotic fractures, especially in elderly patients.