The absorption profile and availability of a physiological subcutaneously administered dose of recombinant human growth hormone (GH) in adults with GH deficiency

AIMS: To investigate the absorption profile and estimate the bioavailability of three doses of recombinant human growth hormone (rhGH) smaller than 2 IU in females with GH deficiency (GHD). A second aim of the study was to compare the mean 24 h GH concentrations after s.c. injection of rhGH with the physiological mean 24 h GH concentration of healthy females of comparable age, height, and BMI. METHODS: Fourteen female patients with substituted GHD, and 14 healthy females of comparable age, height, and BMI were studied. All GHD patients underwent 24 h GH sampling after s.c. injection of rhGH in doses of 0.6, 1.2, or 1.8 IU. In addition, these patients underwent a 4 h GH sampling after i.v. injection of rhGH (1 IU). In healthy subjects, blood was withdrawn every 10 min for 24 h to determine the physiological GH profile. RESULTS: A s.c. dose of 0.6 IU resulted in a mean and maximum GH concentration of 0.95+/-0.04 mU l(-1) and 2.62+/-0.09 mU l(-1). A doubling (or tripling) of the rhGH dose resulted in a doubling (or tripling) of the mean and maximum GH concentration. The time of maximum GH concentration was reached on average after 261+/-27 min. Mean GH concentration in healthy females was comparable with the mean GH concentration after a s.c. dose of 1.2 IU. Mean availability of the s.c. injected dose was 63%+/-4%. CONCLUSIONS: A dose of 1.2 IU resulted in a mean GH concentration comparable with the mean physiological GH concentration in healthy females of comparable age, height, and BMI.