EVIDENCE OF LOCAL DEGRADATION OF SUBCUTANEOUSLY INJECTED BIOSYNTHETIC HUMAN GROWTH HORMONE IN HYPOPITUITARY PATIENTS

Abstract

In a previous study we observed that subcutaneously (s.c.) injected human growth hormone (hGH) resulted in significantly lower serum growth hormone profiles (AUC) than after intramusculary (i.m.) administration. In the present study we compared the steady state serum concentrations of continuous infused biosynthetic human growth hormone (B-hGH) via the s.c. and i.v. route in 7 hypopituitary subjects, 6 males and 1 female, mean age 21 years (15-29). The rate of B-hGH infusion was 50 ng/kg/min. I.v. infusion was performed for 3 hours, giving a mean steady state concentration of 17.3 ng/ml ± 3.3 (SEM). Following a three hours intermission the s.c. infusion was commenced lasting 19 hours and resulted in significantly lower serum concentration, 5.0 ng/ml ± 1.0 (SEM) (p < 0.001). In four of the subjects the s.c. infusion was extended for a further 24 h with a steady state mean serum concentration of 6 ng/ml (p > 0.2). These findings strongly suggest a local subcutaneous degradation of injected hGH in these subjects. The exact mechanisms cannot be deduced from our results but must await further investigation.