Inhibition effect of atropine on growth hormone

It has been known that the main hypothalamic nuclei, especially the arcuate nucleus, contains acetylcholine, it has also shown that the arcuat nucleus is the main area of GHRH production, with its axons reaching the median eminence to connect with the hypophyseal postal circulation. Atropine, as an anticholinergic agent, can inhibit the synthesis of acetylchine in the arcuate nucleus and then reduce the secretion of GH. Our study illustrated that GH secretion was increased after exercise and the elevated GH level could be inhibited by the administration of atropine in normal subjects. However, while in acromegaly the high basal GH levels could not be inhibited by 100g of glucose loading or 0.6mg of atropine in active phase of the disease. The blood sugar remained unchanged during atropine test. It is thus suggested that atropine test may be used as a GH inhibitory test in acromegaly patient with overt diabetes.