Urinary growth hormone and insulin-like growth factor I: Effects of growth-hormone injection schedule

Urinary growth hormone (GH) and insulin-like growth factor I (IGF-I) excretion profiles were compared in children receiving biosynthetic GH. Group 1 included 18 healthy controls. Group 2 included nine children given biosynthetic GH three times a week. Group 3 included 14 children given daily GH injections. Overnight urine samples were collected for three consecutive nights in all groups. No significant day-to-day variation in urinary GH output was observed in group 1. In group 2, urinary GH output was significantly higher on day one following injection than on days two and three. Urine GH outputs in group 2 were significantly lower on days two and three than the values observed on all days in group 3. Throughout the three- day study, subjects in group 3 excreted similar amounts of GH significantly higher than those of controls. Urinary IGF-I output (nmol/kg) was similar on all three study days in groups 1 and 3. Group 2 had significantly lower urinary IGF-I output on day three compared with day one. Urinary IGF-I output on day three was also significantly lower in group 2 than in group 3. We conclude that urinary GH and IGF-I outputs are influenced by the frequency of GH administration.