The responses of gastric inhibitory polypeptide (GIP), gut glucagon-like-immunoreactivity (gut GLI), insulin, and pancreatic glucagon to a 50-g oral glucose load were studied in late pregnancy and postpartum in 11 normal women, 10 normal weight gestational diabetics, and 10 overweight gestational diabetics. The GIP response to glucose was impaired in pregnancy in all three groups. In pregnancy, the GIP response was smaller in both groups of gestational diabetics than in normal women, whereas postpartum, the GIP response was lower than normal in the normal weight gestational diabetics only. In pregnancy, the gut GLI response to glucose was reduced in the overweight gestational diabetics and abolished in the normal women. The insulin response to glucose was increased in pregnancy in all three groups. Moreover, it was higher in the overweight gestational diabetics than in the other two groups in pregnancy and postpartum. In the normals, the suppression of glucagon levels after glucose ingestion was more marked in pregnancy than postpartum, whereas no such effect was seen in gestational-diabetic pregnancy. It is concluded that pregnancy—normal as well as gestational-diabetic—is accompanied by profound changes in the secretion of gastrointestinal insulinotropic hormones after glucose ingestion. These findings may be important for the understanding of changes in metabolism and gastrointestinal physiology in gestation.

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