Interdependence of lean body mass and total body water, but not quality of life measures, during low dose GH replacement in GH-deficient adults

Abstract

Lean body mass (LBM) and total body water (TBW) are reduced in GH-deficient (GHD) adults and alter with GH replacement. Whether these parameters are interdependent and whether alterations in their homeostasis contribute to the perceived quality of life (QOL) deficit in GHD remains unclear. In this study, IGF-I, body composition by whole-body dual-energy X-ray absorptiometry, TBW by deuterium dilution (D(2)O) and two validated QOL instruments - psychological general well-being schedule (PGWB, generic, 6 domains; lower score worse QOL) and assessment of GH deficiency in adults (AGHDA, disease orientated; higher score worse QOL) were studied at baseline and after 3 and 6 months of GH replacement in thirty GHD adults. Patients with diabetes insipidus, and cardiac and renal failure were excluded. Median age-adjusted IGF-I standard deviation score increased from -3.40 (-6.40 to -1.60) to -0.2 (-1.88 to 0.78) (P < 0.0001) at a median daily GH dose of 0.4 mg. During treatment, LBM increased from 47.4 +/- 10.7 kg at baseline to 49.5 +/- 10.8 kg at 6 months (P = 0.0008), and fat mass decreased from 28.0 +/- 12.1 kg at baseline to 27.2 +/- 12.6 kg at 6 months (P = 0.0004). A non-significant trend towards an increase in TBW was observed (mean 1.7 kg, P = 0.08). The PGWB score increased from 62.9 +/- 20.6 to 73.7 +/- 21.7 (P = 0.0006). The AGHDA score decreased from 13.7 +/- 7.3 to 8.75 +/- 7.75 (P = 0.0002). At each time point, a linear correlation between LBM and TBW was demonstrated, defined by TBW = (0.972 x LBM)-10.6. However, only a weakly positive correlation existed between the percentage changes in these variables (R = 0.40, P = 0.04). No correlations were demonstrated between QOL measures and body composition. The change in LBM with physiological GH replacement correlates weakly with change in TBW, therefore factors other than TBW may also contribute to the LBM changes. Improved QOL with GH replacement is not explained by favourable changes in body composition.