Body fluids, circadian blood pressure and plasma renin during growth hormone administration: a placebo-controlled study with two growth hormone doses in healthy adults

Abstract

Side effects that can be related to fluid retention are common during the initial phases of growth hormone (GH) administration. The aim of this study was to examine the changes in body fluid compartments, diurnal blood pressure and plasma renin concentration during GH administration with two different dosages in healthy adults. Eight healthy male subjects aged 24–32 years were examined during three 2-week study periods in a double-blind placebo controlled study. They received, in random order, GH (3 or 6 IU m⁻² daily) or placebo during 2 weeks. Bio-impedance was measured every 2nd day, and extracellular volume (ECV) and plasma volume (PV) were isotopically determined at day 6. Blood samples were obtained regularly. Diurnal blood pressure was recorded and 24-h urinary samples were collected at days 0, 6 and 14. ECV (1) was increased by GH (placebo, 19.58 ± 0.82; 3 IU m⁻², 20.77 ± 1.22; 6 IU m⁻², 20.65 ± 0.94; p<0.01), whereas PV (1) was unaffected (placebo, 3.91 ± 0.20; 3 IU m⁻², 4.04 ± 0.22; 6 IU m⁻², 3.90 ± 0.27). Total body water (1) increased significantly during GH administration (placebo, 50.8 ± 2.6; 3 IU m⁻², 52.6 ± 2.3; 6 IU m⁻², 53.9 ± 1.8, p<0.05). After 6 days of treatment a significant increase in renin (p = 0.03) was observed. Mean diurnal blood pressure levels remained unchanged, whereas mean diurnal heart rate (min⁻¹) increased significantly (placebo, 75 ± 3.6; 3 IU m⁻², 79 ± 3.2; 6 IU m⁻², 79 ± 3.7; p<0.01). In conclusion, GH administration induces an elevation in total body water which may involve a stimulation of plasma renin and an increased ECV without any changes in PV or diurnal blood pressure.

Key Words:

• diurnal blood pressure
• extracellular volume
• growth hormone
• plasma volume
• renin
• total body water