The effect of acute administration of human growth hormone (HGH) and of alpha-melanocyte stimulating hormone (alpha-MSH) on plasma aldosterone, cortisol, corticosterone and growth hormone has been studied in normal man and in patients with panhypopituitarism. There is no acute effect of exogenous HGH on plasma levels of aldosterone, cortisol and corticosterone in normal man and in patients with panhypopituitarism. The plasma level of immunoreactive HGH measured during acute HGH infusion in man does not seem to be proportional to the dose administred in our study. Alpha-MSH raises the concentartion of plasma HGH, BYT THIS STIMULATION IS NOT DOSE-DEPENDENT. Aldosterone, cortisol and corticosterone concentrations are not influenced by the elevation of HGH mediated by alpha-MSH in normal man. Although in some patients with panhypopituitarism an elevation of plasma aldosterone concenntration following alpha-MSH infusion is observed, it is unlikely that MSH is directly involved in the acute regulation of aldosterone secretion in healthy subjects.