Synthetic human pancreatic growth hormone-releasing factor (hpGRF1–44) was given as an i.v. bolus to 8 healthy volunteers in 5 different dosages. Blood was collected before and up to 120 min after GRF-injection. Four subjects received only placebo, five received 3.3 µg, three 12.5 µg, four 50 µg, 5 received 100 µg, and three 200 µg hpGRF1–44. No serious side effects were recorded after hpGRF1–44. All dosages with the exception of the 3.3 µg-dosage lead to a clearcut and significant increase of GH-levels with a maximum occurring 15 to 30 minutes after hpGRF1–44. A dose-response-relationship between the injected GRF-dosage and growth hormone levels was only found from 3.3 to 50 µg hpGRF1–44. The administration of 100 or 200 µg hpGRF1–44 did not lead to a further increase of GH-levels compared to the 50-µg-dose. This was in contrast to the clearcut dose dependency of hpGRF1–44-levels measured by a specific radioimmunoassay over the whole dose range with a maximum occurring 5 minutes after the injection. The mean halftime of disappearance for the 200-µg-dose of hp-GRF1–44 was 7.6±1.7 minutes (±SE). We conclude that there is a marked heterogeneity of the GH-response to hpGRF1–44 in healthy volunteers though a dose-response-relationship over the range from 3.3 to 50 µg hpGRF i.v. could be established. The dose-response-dependency of hpGRF1–44-levels up to the 200-µg-dose indicates that the maximal GH-response is reached when 50 µg hpGRF1–44 are administered. Therefore the test for routine purposes should be performed with 50 µg or 1 µg/kg body weight i.v.
- Growth hormone
- Growth hormone-releasing factor (GRF)
- Radioimmunoassay of GRF and GH
ASJC Scopus subject areas