Bone mass and bone exchange were studied in 10 post menopausal females (age 36 +/- 9) with hyperthyroidism due to Graves disease dating from over 6 months. Biphoton osteodensitometry of the lumbar spine and hips, calcium intake, hematocrit, hemoglobin and 24 hr urinary calcium excretion were determined in each patient and compared to a control group. Hyperthyroid patients had a lower calcium intake, and evidence of higher bone turnover. However, bone density was not different from control. There was a strong correlation of bone density with serum calcium (r 0.72) and T3 levels (r 0.68). Thus, untreated hyperthyroidism associated to Graves disease does not lead to decreased bone mass in a 6 month period.