COMPARISON OF DIFFERENT BODY-COMPOSITION MODELS IN ACROMEGALY

The aberrant body composition of 10 patients with active acromegaly wa s used to evaluate the validity and limitations of several models and methods to assess body composition. Body composition was determined us ing either a two-compartment model, dividing the body in a body fat (B F) compartment and a fat-free mass (FFM) compartment, or a four-compar tment model in which the FFM compartment comprises the three following components: body cell mass, extracellular water and the fat-free extr acellular solids. The measurement techniques consisted of anthropometr y, bioelectrical impedance analysis (BIA) - applying various establish ed regression equations - tritiated water dilution, whole body K-40-co unting, and whole body computed tomography (CT). This latter method wa s used as the reference technique. Assessment of total body water usin g BIA - applying the RJL or Kushner equation - correlated significantl y with the assessment using tritiated water dilution (P < 0.01). Body fat assessment using the two-compartment model based on either tritiat ed water dilution or BIA - applying the RJL or Lukaski equation - as w ell as body fat assessment using the four-compartment model based on t ritiated water dilution and whole body K-40-counting were significantl y correlated with body fat assessment using CT (P < 0.01) and resulted in good agreement with each other with respect to the absolute values of the body fat determination. BIA using other regression equations o verestimated body fat by 7.2-13.7 kg. Whole body K-40-counting was sig nificantly correlated with CT-determined muscle plus skin volume (P < 0.001). CT-calibrated anthropometric predictions significantly overest imated body fat. It is concluded that in patients with active acromega ly, the determination of body composition using either certain two-com partment models based on measurement of total body water or bioelectri cal impedance, or a four-compartment model based on total body water a nd total body potassium measurements show good agreement with CT-deter mined body composition.