OBJECTIVE In adults, there are few data regarding GH responses to provocative stimuli other than insulin‐induced hypoglycaemia. We have compared the GH response to four different growth hormone secretagogues and placebo in normal healthy adult males.DESIGN This was a prospective, randomized, placebo‐controlled study in 18 normal male subjects. After an overnight fast, an intravenous cannula was inserted into the arm of each subject and a blood sample was taken for GH at −30, −15, and 0 minutes. Four provocative agents (intravenous insulin 0.2 IU/kg; intravenous arginine 20 g/m2as an infusion over 30 minutes; oral clonidine, either 100 or 200 μg; intramuscular glucagon 1 mg) and placebo were administered to each subject in a randomized manner on different days. Further blood samples were taken at 15‐minute intervals for 180 minutes for GH estimation.RESULTS The median (range) GH peak response for each agent was insulin 107.7 (28.1–200) mU/l; arginine 22.3 (3.1–72.9) mU/l; glucagon 42 (11.8–200) mU/l; 100 μg clonidine 7.2 (<1–22.2) mU/l; 200 μg clonidine 8.2 (1.1–88) mU/l and placebo 2.4 (<1–30.2) mU/l. The peak GH response to insulin‐induced hypoglycaemia (ITT) was significantly greater than for any other agent (P<0.0001). The peak GH response to glucagon was significantly greater than for arginine (P<0.05), clonidine at 100 and 200 μg (P<0.01) and placebo (P<0.01). The peak GH response following administration of arginine was significantly greater than for clonidine 100 and 200 μg (P<0.05), and placebo (P20 mU/l to glucagon, arginine and clonidine respectively. In complete contrast only one subject achieved a peak response of less than 40 mU/l (28.1 mU/l) to ITT.CONCLUSIONS The most profound GH release is seen after insulin‐induced hypoglycaemia. Glucagon appears to be more effective at inducing GH release than