Pyridostigmine, an Acetylcholinesterase Inhibitor, Stimulates Growth Hormone Release, but has no Effect on Basal Thyrotrophin or Adrenocorticotrophin Levels, or the Thyrotrophin Response to Thyrotrophin-Releasing Hormone

Pyridostigmine, an acetylcholinesterase inhibitor, stimulates growth hormone (GH) release and is thought to act by inhibiting hypothalamic somatostatin release. There are few data concerning the effect of pyridostigmine on other pituitary hormones apart from GH. We have studied the effect of pyridostigmine on basal GH, thyrotrophin (TSH), prolactin, adrenocorticotrophin and cortisol release, and thyrotrophin-releasing hormone (TRH)-stimulated TSH and prolactin release, in two studies involving nine healthy male subjects. Pyridostigmine stimulated GH release in all subjects but had no effect on adrenocortocotrophin or cortisol levels, or basal or TRH-stimulated TSH and prolactin levels. There are some data to suggest that somatostatin inhibits TRH-stimulated TSH release. Our findings, however, suggest that either endogenous somatostatin tone has little effect on the TSH response to TRH compared to its effects on GH or pyridostigmine acts through a mechanism other than altering somatostatin tone. Pyridostigmine did not alter adrenocorticotrophin or cortisol levels in the presence of a clear action on GH release, providing further evidence that the previously reported effects of cholinergic drugs on cortisol release are stress-related.