Breast feeding-induced effects on plasma gastrin and somatostatin levels and their correlation with milk yield in lactating females

Abstract

Maternal gastrin and somatostatin levels have been shown to be influenced during suckling in dogs and pigs. The present study was performed to investigate whether the levels of gastrin and somatostatin are influenced by breast feeding in lactating women. Repeated blood samples were drawn in connection with nursing in 15 females and plasma levels of gastrin and somatostatin were measured by radioimmunoassay. Gastrin levels rose significantly ( P = 0.01) within two minutes after onset of suckling. Somatostatin levels either decreased or increased as an effect of breast feeding. The direction of the change was correlated to the pre-suckling somatostatin levels ( P < 0.01). The somatostatin level recorded 60 min after start of breast feeding was significantly lower than basal levels ( P < 0.01) indicating a longterm inhibitory effect on somatostatin secretion. The suckling-induced effect on somatostatin levels was correlated with the amount of milk ejected (R s − 0.52, P < 0.05). The mechanism by which suckling influences circulating gastrin and somatostatin levels is unknown, but we suggest that suckling leads to a reflex activation of the vagal nerves, which influence the release of these hormones from the stomach. The size of the gastrointestinal tract is increased during pregnancy and lactation, illustrating that the maternal digestive capacity is adapted to the high demand for energy intake occurring during lactation. We speculate that the suckling stimulus enhances gastric functions by influencing the release of gastrin and somatostatin, which stimulate and inhibit gastric functions and growth, respectively. Whether the correlation between the effect on somatostatin levels and milk yield reflects a direct effect of this peptide in the mammary gland or whether it just reflects parallel suckling-induced effects on milk secretion and somatostatin secretion is not known.