Estimating body fat and lean tissue distribution in hyperthyroidism by dual-energy X-ray absorptiometry.

Body composition (fat mass, lean tissue, and bone mineral content), was determined by dual-energy X-ray absorptiometry (DEXA) at baseline and 6, 12, and 24 mo after treatment of hyperthyroidism. Ten women with Graves' disease were included in this study. Suppressed serum TSH and high total serum thyroxine levels were found in all patients. The patients received antithyroid therapy (methimazol and/or (131) I radioiodine). Lean tissue, bone mass, and body weight increased after 2 yr of euthyroidism. Total body lean mass increased from 32.3+/-3.9 kg to 35.2+/-4.1 kg (p < 0.005). Total lean mass increased from 10.6 +/- 1.8 kg to 11.6 +/- 1.9 kg (p < 0.01) in the legs, from 3.6 +/- 0.8 kg to 4.0 +/- 0.7 kg (p < 0.02) in the arms, and 16.0 +/- 1.6 kg to 17.4+/-1.8 kg (p < 0.005) in the trunk. Total-body fat mass increased from 19.9 +/- 6.6 kg to 21.2 +/- 7.6 kg (ns). At 1-yr, regional analysis disclosed that fat mass had increased in the trunk from 8.9 +/- 2.9 kg to 10.9 +/- 3.9 kg (p < 0.04) and from 2.3 +/- 0.9 kg to 3.2 +/- 1.2 kg in the arms (p < 0.04). After 2 yr of treatment, fat tissue remained unchanged in all of the studied regions. The results obtained herein suggest that, compared to initial values, the treatment of hyperthyroidism restore body weight. This increase is mainly the result of recovery of lean mass, predominantly in the limbs and trunk. This study provides new data on the patterns of change in body composition occurring in hyperthyroid patients during a 24-mo follow-up after attaining euthyroidism.