Which hormone is involved in the regulation of GI motility?

Cholecystokinin (CCK) plays a significant role in the regulation of gastrointestinal motility. It is a peptide hormone secreted by the cells in the duodenum in response to the presence of fats and proteins in the chyme. Once released, CCK has several important effects on the digestive system, including stimulating the gallbladder to contract and release bile, which is essential for fat digestion.

Moreover, CCK enhances the secretion of pancreatic enzymes that aid in digestion, and it also slows gastric emptying. This delayed movement of food from the stomach to the small intestine provides the time needed for the digestive enzymes to effectively break down food, thereby optimizing nutrient absorption.

In contrast, hormones like thyroxine, cortisol, and epinephrine serve functions not primarily focused on GI motility. Thyroxine mainly regulates metabolism, cortisol is involved in stress responses and metabolic processes, and epinephrine is associated with the "fight or flight" response, which can inhibit gastrointestinal activity rather than promote it. Thus, understanding the specific role of cholecystokinin highlights its key function in managing the digestive process and facilitating efficient GI motility.