The study shows that salmon calcitonin (a hormone used for bone health) reduces the growth hormone boost you get from a GHRH peptide like sermorelin. Taking pyridostigmine, a drug that raises acetylcholine, can increase the GH response to GHRH, but it doesn’t counteract the calcitonin effect. In short, calcitonin can blunt the benefits of GHRH, while pyridostigmine may help a bit if calcitonin isn’t involved.

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.