Peptide YY

Peptide YY is a hormone made in the small intestine. It helps to reduce appetite and limit food intake.

Alternative names for peptide YY

PYY; peptide tyrosine tyrosine; pancreatic peptide YY3-36; pancreatic peptide YY

What is peptide YY?

The full name for peptide YY is pancreatic peptide YY. It is a hormone that is secreted from endocrine cells called L-cells in the small intestine. There are two major forms of the peptide; one is 36 amino acids long (PYY1-36) and the other lacks the first two amino acids (PYY3-36). It is secreted alongside the hormone glucagon-like peptide 1. Peptide YY is released after eating, circulates in the blood and works by binding to receptors in the brain. Binding of peptide YY to brain receptors decreases appetite and makes people feel full after eating. Peptide YY also acts in the stomach and intestine to slow down the movement of food through the digestive tract.

How is peptide YY controlled?

Peptide YY secretion is mainly stimulated by the presence of food in the digestive tract, particularly fat and protein. The amount of peptide YY that is released into the blood depends on the amount of calories eaten, with higher calorie foods causing more peptide YY release than lower calorie foods. Peptide YY secretion can also be stimulated by digestive juices (such as bile) and another gastrointestinal hormone called cholecystokinin. The highest levels of peptide YY are found in the second hour after eating. Peptide YY levels then gradually decrease. Low levels of peptide YY are seen during long periods without eating, for example overnight.

What happens if I have too much peptide YY?

High peptide YY concentrations are unusual. They will cause a decrease in appetite and food intake. High peptide YY concentrations are associated with diseases where there is dramatic weight loss, such as anorexia nervosa, coeliac disease, inflammatory bowel disease (Crohn’s disease and ulcerative colitis) and some cancers.

What happens if I have too little peptide YY?

Low peptide YY concentrations are associated with an increase in appetite and food intake. Low peptide YY levels are seen in obesity and before the onset of type 2 diabetes and may contribute to weight gain in these conditions. However, low peptide YY concentrations are very unlikely to be the main cause of obesity as the levels decrease after weight gain has started. There has been some research into using peptide YY as a medication for obesity, aiming to decrease the appetite of people who are overweight. This research is still ongoing.

It is extremely rare to have a genetic (inherited) deficiency of peptide YY.

Last reviewed: Mar 2021