Effect of dopamine infusion on plasma levels of growth hormone in normal subjects and in agromegalic patients.

In ten normal subjects and in twenty acromegalic patients plasma levels of growth hormone were studied after administration of L-dopa and a dopamine infusion. In the ten normal subjects L-dopa, but not dopamine, increased plasma levels of GH. In the acromegalic patients both L-dopa and dopamine were followed by an inhibition of GH release. Since dopamine does not cross the blood-brain barrier, these results, although not excluding a site of action at median eminence level, support the thesis that the inhibitory effect of dopaminergic stimulation on GH release in acromegaly possibly involves receptors present on GH-secreting cells.