Possible role of glucagon in cyproheptadine-induced increase of insulin secretion.

In order to test the hypothesis that insulin secretion may be affected by increased glucagon levels during cyproheptadine (CPH) administration, an arginine-glucose test was performed in 8 normal women and repeated after three days of CPH administration at a dose of 16 mg/day. Both the glucagon and the insulin response were increased by CPH treatment and so were their incremental areas. For glucagon, the increase was present at all times tested, for insulin this rise was significant only during the first 60 min of the arginine test and during the rapid secretory phase following glucose injection. The difference between the incremental areas of glucagon before and after CPH treatment was significantly correlated to the above mentioned insulin areas and to insulin peak values. These data are in agreement with the hypothesis that in vivo CPH action on insulin secretion may be partly mediated by its effects on circulating glucagon levels.