Gastric Inhibitory Polypeptide (GIP) Stimulation by Oral Glucose in Man

Abstract
Gastric inhibitory polypeptide (GIP) was measured by a specific radioimmunoassay in 25 normal subjects who received 75 g of oral glucose or 25 g intravenously. Serum GIP levels increased in every subject after oral glucose ingestion. The mean fasting GIP was 319 ± 18 pg/ml and increased to a mean peak response of 747 ± 59 pg/ml between 15 and 60 min after oral glucose. In contrast, intravenous glucose did not significantly stimulate GIP release. We conclude that oral glucose is a potent stimulus for the enteric release of GIP.