Long-term effects of growth hormone (GH) on body fluid distribution in GH deficient adults: a four months double blind placebo controlled trial

Objective: Short-term growth hormone (GH) treatment normalises body fluid d istribution in adult GH deficient patients, but the impact of long-term tre atment on body fluid homeostasis has hitherto not been thoroughly examined in placebo controlled trials. To investigate if the water retaining effect of GH persists for a longer time we examined the impact of 4 months GH trea tment on extracellular volume (ECV) and plasma volume IPV) in GH deficient adults. Design: Twenty-four (18 male, 6 female) adult GH deficient patients aged 25 -64 years were included and received either GH (n=11) or placebo (n=13) in a double blind parallel design. Methods: Before and at the end of each 4 month period ECV and PV were asses sed directly using Br-82- and I-125-albumin respectively and blood samples were obtained. Results: During GH treatment ECV increased significantly (before: 20.48+/-0 .991, 4 months: 23.77+/-1.381 (P<0.01)), but remained unchanged during plac ebo administration (before: 16.92+/- 1.011, 4 months: 17.60+/-1.241 (P=0.37 )). The difference between the groups was significant (P<0.05). GH treatmen t also increased PV (before: 3.39+/-0.271, 4 months: 3.71+/-0.261 (P=0.01)) , although an insignificant increase in the placebo treated patients (befor e: 2.81+/-0.181, 4 months: 2.89+/-0.201 (P=0.37)) resulted in an insignific ant treatment effect (P=0.07). Serum insulin-like growth factor-I increased significantly during GH treatment and was not affected by placebo treatmen t. Plasma renin (mIU/l) increased during GH administration (before: 14.73+/ -2.16, 4 months: 26.00+/-6.22 (P=0.03)) and remained unchanged following pl acebo (before: 20.77+/-5.13, 4 months: 20.69+/-6.67 (P=0.99)) leaving no si gnificant treatment effect (P=0.08), Conclusion: The long-term impact of GH treatment on body fluid distribution in adult GH deficient patients involves expansion of ECV and probably also PV. These data substantiate the role of GH as a regulator of fluid homeost asis in adult GH deficiency.