Effects of calcitonin on GH response to pyridostigmine in combination with hGHRH (1-29) NH2 in normal adult subjects.

Studies in man demonstrated that salmon calcitonin (sCT) administration blunts the pituitary GH response to GH-releasing hormone (GHRH). However, the mechanisms underlying this inhibitory action of CT in man are unclear. Pyridostigmine (PD), an acetylcholinesterase inhibitor, is hypothesized to enhance the GH response to GHRH in normal subjects probably via a decrease in the somatostatinergic tone. The aim of the present study was to investigate the mechanism of the inhibitory action of sCT on the GH response to human GHRH (1-29) NH2 by concomitant PD administration in normal humans. The GH response to GHRH was significantly suppressed by prior administration of sCT. Pretreatment of subjects with PD significantly enhanced the GH response to GHRH but did not alter the inhibitory actions of sCT. We conclude that sCT is able to inhibit GHRH-stimulated GH secretion in man without influencing the hypothalamic somatostatinergic tone.