USING DILUTION TECHNIQUES AND MULTIFREQUENCY BIOELECTRICAL-IMPEDANCE TO ASSESS BOTH TOTAL-BODY WATER AND EXTRACELLULAR WATER AT BASE-LINE AND DURING RECOMBINANT HUMAN GROWTH-HORMONE (GH) TREATMENT IN GH-DEFICIENT ADULTS

Due to the use of various, and mostly indirect, methods to estimate to tal body water (TBW) and extracellular water (ECW), there is no agreem ent about whether body water distribution, i.e. the ECW to TBW ratio, is normal in GH-deficient (GHD) subjects at baseline and during recomb inant human GH (rhGH) treatment. We studied body water distribution in 14 patients with adult-onset GHD and in 28 healthy controls. We also investigated the effect of GH replacement therapy for 4 and 52 weeks o n body water distribution. All patients started with a dose of 0.6 IU rhGH/day for the first 4 weeks. After 52 weeks, the dose varied betwee n 0.6-1.8 IU/day. TBW and ECW were measured by dilution of deuterium a nd bromide, respectively. Both parameters were also estimated using mu ltifrequency bioelectrical impedance (BIA). Patients with GHD had sign ificantly lower ECW and TBW than healthy controls. In addition, the EC W to TBW ratio was significantly lower in GHD patients than in healthy controls. Four weeks of GH treatment significantly increased body wei ght, TBW, ECW, and ECW/TBW. A further increase in TBW, but not ECW; wa s found after 52 weeks of treatment. The mean increases in TBW and ECW from the baselines were 2.5 +/- 0.3 and 2.0 +/- 0.3 L, respectively. The correlation coefficient and the estimated reliability between meas ured and estimated TBW and ECW at any time point were all high (>0.91 and >0.95, respectively). In general, both ECW and TBW were overestima ted by multifrequency BIA in GHD adults. During treatment, the overest imation of both ECW and TBW diminished. The estimation error was corre lated with the level of the body water compartment and the ratio of EC W to TBW. The estimated change in ECW with rhGH treatment was underest imated by multifrequency BIA. We conclude that GHD adults have lower E CW and TBW and a lower ECW to TBW ratio, as measured by dilution techn iques. The ECW to TBW ratio can be normalized within 4 weeks of rhGH t reatment at a dose of 0.6 IU/day. Finally, we conclude that multifrequ ency impedance measurements do not give valid estimates of body water compartments in the follow-up of patients with GHD.