Assessment of hydration by means of bioelectrical impedance and arm muscle area during growth hormone (GH) replacement therapy: A prospective study of 130 GH-deficient patients

ObjectiveGrowth hormone (GH)-deficiency is associated with a reduced extracellular volume (ECV), whereas GH replacement may cause fluid retention. We have tested a simple method to assess hydration in GH-deficient patients (GHD) based on concomitant measurements of body resistance by bioelectrical impedance analysis (BIA), and arm muscle area (AMA).DesignWe prospectively followed 130 patients (54 females, 76 males) with adult-onset GHD before and during 1–5 years GH replacement therapy.MethodsConcomitant measurements of body resistance and AMA were done on four occasions: before treatment, after one month and one year of treatment, and at the most recent visit. Based on normative data obtained in 142 women and 84 men an inverse relationship was documented between body resistance and AMA. Assuming that linear height and the concentration of electrolytes remain constant, body resistance at a given AMA will reflect specific hydration.ResultsIn the patients a gender-specific inverse correlation between body resistance and AMA existed, which was different from the control group and changed during GH replacement. A deviation between predicted (based on normative data) and measured body resistance at a given AMA was recorded in the patients before and during therapy compatible with relative dehydration in the untreated state followed by an increase in hydration during therapy.ConclusionsConcomitant measurements of BIA and AMA in GHD patients may provide a non-invasive and simple means to estimate hydration before and during GH replacement.