Influence of pyridostigmine on growth hormone (GH) response to GH-releasing hormone pre- and postprandially in normal and obese subjects.

The effect of pyridostigmine (PYR), an inhibitor of acetylcholinesterase, on the GH response to GH-releasing hormone (GHRH) before and after a meal was studied in 14 normal subjects (8 females and 6 males) and 21 obese subjects (13 females and 8 males). In normal subjects tested in a fasting state, PYR was capable of stimulating GH secretion and increasing the GH response to GHRH. These effects were not apparent after food, suggesting a reduction in cholinergic hypothalamic activity. In obese subjects tested in a fasting state, PYR was ineffective when administered alone. On the contrary, it was able to increase the GH response to GHRH. After food, the augmenting effect of PYR on the GH response to GHRH was not observed, whereas a delayed inhibition of the GH response was found after PYR plus GHRH treatment. Our findings support the hypothesis that cholinergic hypothalamic activity plays a pivotal role in impaired GH regulation and the altered sensitivity of GH secretion to metabolic fuels in obese subjects.