Digestion and Appetite Hormones – How the Gut Talks to the Body

Many hormones regulate digestion and appetite, and this video shows you how to make an easy chart to organize facts about the main hormones. Watch the video below, read the summary, and check out the tips for remembering the hormones. Citations for the video information are listed at the end.


Gastrin is secreted in the stomach and causes the release of gastric lipase and hydrochloric acid.

Tip to remember: “gastrin” shares the same root as “gastric” which means “stomach.” It is the main hormone in the stomach, where the body begins to digest protein and fats. To do this, it needs lipase and HCl.


Secretin is released in the small intestine in response to acidic chyme. It causes the pancreas to secrete bicarbonate to neutralize the acid.

Tip to remember: I like to think of secretin as the “secret agent” that has to “neutralize” the bad guy. Maybe I watch a lot of spy shows : )

Cholecystokinin (CCK)

CCK stimulates pancreas to release lipase and gallbladder to release bile. 

Tip to remember: The root “cholecysto” means gallbladder, and “kinan” sounds like “kinetic” which means movement. So I think of CCK as the hormone that gets the gallbladder to kick into gear.

Glucose-dependent insulinotropic polypeptide (GIP)

GIP is an incretin, which is a hormone that stimulates insulin secretion.

Tip to remember: if you can remember GIP’s full name, you can remember what it does. But remember that it’s not gastric inhibitory peptide anymore!

Glucagon-like peptide-1 (GLP 1)

GLP and GIP act on beta cells of the pancreas to stimulate insulin secretion and inhibit glucagon secretion by the alpha cells. 

Tip to remember: because it is “glucagon-like” it can trick the pancreas into thinking you’ve already secreted glucagon, so it won’t make more.


Ghrelin stimulates the hypothalamus to induce hunger. Ghrelin levels decrease less after a fat-based meal than carb or protein-based meals. 

Tip to remember: a classic trick, think of “the hungry gremlin”

Peptide YY

PYY turns off the feeling of hunger, and it reaches its peak level about 1 to 2 hours after meal initiation.

Tip to remember: ok this one’s a little silly (but it works!): I like to pretend “YY” stands for “yum yum” because it’s released after you eat

Links to Resources

Appetite Regulation: Hormones, Peptides, and Neurotransmitters and Their Role in Obesity: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6796227/

The role of gastrointestinal hormones in the pathogenesis of obesity and type 2 diabetes: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4108747/#CIT0045

Physiology, Gastrin – StatPearls – NCBI Bookshelf: https://www.ncbi.nlm.nih.gov/books/NBK534822/

The physiological roles of secretin and its receptor: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4200670/

Cholecystokinin: http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/gi/cck.html

Effects of CCK on pancreatic function and morphology. – PubMed – NCBI: https://www.ncbi.nlm.nih.gov/pubmed/8185159

Mechanisms of CCK signaling from gut to brain: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2692370/

Amino acids stimulate cholecystokinin release through the Ca2+-sensing receptor: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3074989/

The Role of Incretins in Glucose Homeostasis and Diabetes Treatment: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2696340/

Ghrelin: much more than a hunger hormone: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4049314/

Structure, regulation and function of ghrelin | The Journal of Biochemistry | Oxford Academic: https://academic.oup.com/jb/article/151/2/119/2182660#33751450

The gut hormone peptide YY regulates appetite. – PubMed – NCBI: https://www.ncbi.nlm.nih.gov/pubmed/12851312

The role of peptide YY in appetite regulation and obesity: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2670018/