What substance is secreted in response to an oral glucose load?

The correct answer is the substance known as glucose-dependent insulinotropic peptide (GIP). This hormone is secreted by the K cells in the duodenum and jejunum in response to the presence of glucose in the gastrointestinal tract. When you consume an oral glucose load, GIP is released into the bloodstream and stimulates the pancreas to secrete insulin. This mechanism serves to help lower blood glucose levels after a meal by promoting glucose uptake into the cells.

GIP also plays a role in inhibiting gastric motility and acid secretion, which aids in the coordination of digestion following food intake. Its secretion is part of the incretin effect, where hormones released from the gut enhance insulin secretion in response to meals, particularly those containing carbohydrates.

In contrast, insulin is primarily secreted by the beta cells of the pancreas in direct response to elevated blood glucose levels, while secretin is involved in regulating the secretion of digestive fluids in response to acidic chyme from the stomach. Gastrin, on the other hand, is secreted in response to food intake as well, but its primary role is to stimulate gastric acid secretion and digestive processes in the stomach rather than directly responding to glucose intake. This distinction helps clarify why GIP is specifically triggered by an oral glucose load