Cholecystokinin

What is cholecystokinin?

Cholecystokinin is a hormone that functions as part of your digestive system. It’s released (secreted) by your small intestine during the digestive process. It's sometimes called pancreozymin. Cholecystokinin is also found in your brain and central nervous system, though its function there isn't as well understood.

What triggers cholecystokinin to release?

Food passing from your stomach into the first part of your small intestine (duodenum) triggers the next stage of the digestive process. When cells in the mucosal lining of your duodenum (called I-cells) detect the presence of proteins and fats to digest, they trigger cholecystokinin to release into circulation.

What does cholecystokinin do?

Cholecystokinin has several functions at this stage of the digestive process:

• It stimulates your gallbladder to contract and release bile into your small intestine. (“Cholecystokinin” means to “move the gallbladder.")
• It stimulates your pancreas to release pancreatic enzymes. (This is what its other name, “pancreozymin,” means.)
• Bile salts and digestive enzymes help to break down proteins and fats into smaller molecules that can be absorbed in your small intestine. While this is going on, cholecystokinin suppresses gastric emptying so your stomach won’t deliver any more food until the first batch is done.
• It also suppresses your appetite while you’re digesting, by making your stomach feel physically full and by activating vagal nerves in your stomach wall.
• Finally, it triggers peristalsis, the muscle contractions that move food along through your intestines to continue the digestive process.

In the brain and central nervous system, cholecystokinin appears to play a role in anxiety and panic disorders. Studies have shown that elevated levels of cholecystokinin in the brain increase anxiety.

Cholecystokinin has also been reported to have a role in thermoregulation. It is reported to mediate fever when injected in the brain and hypothermia when injected peripherally. More studies are needed to explore this.

Where is cholecystokinin located in the body?

Like other hormones, cholecystokinin circulates in your bloodstream. It communicates with different parts of your body through receptors in the cells of your tissues. In your digestive system, cholecystokinin (CCK) receptors are found in the muscles of your gallbladder, the mucosal lining of your stomach and intestines, and the lining of your pancreas. Receptors are also found in areas of your brain and central nervous system.

What medical conditions involve cholecystokinin?

Low levels of cholecystokinin have been observed in certain conditions, though it’s not clear whether this is a symptom or cause. It may be involved in impaired gastric emptying (gastroparesis) and impaired gallbladder function (biliary dyskinesia). Scientists are also investigating how variations in the cholecystokinin gene may be connected with certain anxiety and metabolic disorders. Some research suggests that genetic variations may affect the way cholecystokinin interacts with the brain to modulate anxiety or hunger signals.

How is cholecystokinin associated with obesity?

Scientists are investigating possible connections between cholecystokinin and obesity. People who carry a particular variant of the cholecystokinin gene appear to have an increased risk of obesity (60%). There is also some evidence that people with clinically severe obesity (class III) are less sensitive to cholecystokinin. Cholecystokinin acts together with another hormone called leptin to regulate hunger signals. People with obesity may have an imbalance of hunger and satiety signals in their brains.

What is a cholecystokinin test?

A cholecystokinin test uses cholecystokinin to stimulate your gallbladder to contract. It’s sometimes done as part of an imaging exam of your gallbladder and biliary system called a HIDA scan. This is a type of nuclear medicine imaging test that produces images of your biliary system by detecting radiation in your body. For the procedure, a technician injects a radioactive isotope (a tracer) into your vein. The tracer travels to your liver and biliary system, and a computer scanner reads it and produces images on a screen.

If your healthcare provider wants to see what happens when your gallbladder contracts, they'll add cholecystokinin as an extra step in the test. The technician will inject cholecystokinin into your vein and follow up with another series of images. The cholecystokinin injection stimulates your gallbladder in the same way that cholecystokinin in your gut does. Your provider might request a cholecystokinin test to look for problems with the way your gallbladder functions.

What medical treatments involve cholecystokinin?

Cholecystokinin is not directly involved in any medical treatment to date, but it has been used in drug development and testing. For example, researchers are attempting to create hunger-suppressing drugs that mimic the effects of cholecystokinin. A particular fragment of cholecystokinin called CCK-4 is known to produce anxiety and panic in humans. For this reason, scientists often use it to test new anxiety-reducing drugs.

A note from Cleveland Clinic

Cholecystokinin plays a fundamental role in digestion, communicating with almost every organ in your digestive system. It’s so reliable as a trigger of gallbladder function that your healthcare provider may use it to examine your gallbladder. It also plays a role in appetite suppression, and cholecystokinin dysfunction may be involved in obesity. Scientists are continuing to investigate the role cholecystokinin plays in the brain and nervous system, including its role in anxiety and panic disorders.