Sex-related differences in gastrin release and parietal cell sensitivity to gastrin in healthy human beings

We compared serum gastrin concentrations and gastric acid secretion basally and in response to a mixed meal in age-matched women and men. Women had significantly higher basal serum gastrin concentrations (P < 0.01) and two- to threefold higher food-stimulated serum gastrin concentrations (P < 0.001) than men. Basal and food-stimulated serum gastrin concentrations in women did not fluctuate significantly during the menstrual cycle. Sex-related differences in food-stimulated serum gastrin concentrations were not due to differences in antral pH because pH after the meal in women and men had been kept constant at 5.0 by in vivo intragastric titration with sodium bicarbonate. Studies using an antibody that reacts only with potent gastrin heptadecapeptide species (G-17-I and II) indicated that women also had threefold higher serum G-17 concentrations after the meal than men (P < 0.005). Elevated serum G-17 concentrations after the meal in women were due to increased release of G-17 rather than slower clearance of G-17 from the circulation.Despite elevated serum gastrin concentrations in response to food, women secreted approximately the same amount of acid relative to their maximal secretory capacity as men. Furthermore, during exogenous G-17 infusion, which led to identical serum gastrin concentrations in women and men, the dose-response curve for acid secretion in women was shifted significantly to the right of the G-17 dose-response curve in men (P < 0.02). The dose of G-17 that stimulated half of peak acid secretion was two to three times higher in women than in men, reflecting significantly reduced sensitivity of parietal cells to gastrin in women (P < 0.05). Our studies suggest that, compared with men, women release greater amounts of gastrin but are at the same time less sensitive to stimulation of acid secretion by gastrin.