Body composition determined by six different methods in women bilaterally adrenalectomized for treatment of Cushing's disease

Abstract

In 14 women, aged 47.2 +/- 10.5 yr, bilaterally adrenalectomized for Cushing's disease 13.6 +/- 7.7 yr before, all receiving conventional doses of glucocorticoid and mineralocorticoid substitution, body composition was studied with regard to body fat, body fat distribution, fat-free mass, and bone mineral density. The data were compared with those of 14 healthy women of similar age, body mass index, and menopausal state. Five different body composition measurement methods were compared, i.e. body densitometry by underwater weighing (UWW), total body water measurement by deuterium dilution (D2O dilution), dual energy x-ray absorptiometry (DXA), bioelectrical impedance spectrometry (BIS), and skinfold measurements, using a four-component model (4C-model) as the reference method. In the patients the percent body fat was significantly higher than that in the controls as determined by all methods, whereas fat-free mass was significantly lower when measured with the 4C-model, UWW, D2O dilution, DXA, or BIS. Measured by DXA, the percent trunk fat, estimated as [fat mass of the trunk (g)/total fat mass (g)] x 100%, was significantly higher in the patients than in the controls (39.3 +/- 6.4% and 29.9 +/- 7.8%, respectively; P < 0.001). Measured by DXA, there was no difference in total bone mineral density between the groups. Differences between the 4C-model, UWW, D2O dilution, and DXA for determination of percent body fat were rather small. Skinfold measurements and BIS results, however, deviated substantially from those obtained using the 4C-model. The study indicates that adrenalectomized patients receiving conventional glucocorticoid substitution have increased body fat percentages with a centripetal fat distribution and lowered fat-free mass, but normal bone mineral density. Furthermore, the study indicates that for clinical practice, DXA, D2O dilution, UWW, and the 4C-model can be used for determination of body composition in this patient group, whereas the more convenient bedside methods, BIS and skinfold measurements, did not give reliable results. We suppose that glucocorticoid overreplacement in adrenalectomized patients might be the cause of their abnormal body composition, although GH deficiency after pituitary surgery could have played a contributory role in some of the patients.