The effect of pyridostigmine (60 mg orally), arginine (0.5 g/kg iv) and propranolol (PROP, 40 mg orally) on GHRH (1 microgram/kg iv)-induced GH release was studied in seven short children. Pyridostigmine and arginine induced a similar potentiating effect on GHRH-induced GH rise (Peak, mean +/- SEM: 56.9 +/- 12.8 and 48.6 +/- 8.5 micrograms/L, respectively vs 12.3 +/- 1.6 micrograms/L; p < 0.05). Combination of GHRH with propranolol induced an increase of GH that was significant only with regard to peak (28.9 +/- 8.4 micrograms/L) but not to AUC. However, GH rises observed after GHRH combined with PD or ARG did not significantly differ from that recorded after coadministration of GHRH and PROP both for peak and AUC. Our results confirm that pyridostigmine and arginine have a striking potentiating effect on the GHRH-induced GH rise in children and show that the tests with GHRH + PD and GH + H + ARG are ore reliable than that with GHRH + PROP to explore the secretory capacity of somatotroph cells.