Cut and paste from New Yorker: The human body produces thousands of peptides. Many are portions of proteins which send messages or regulate systems in the body, often in ways that scientists don’t fully understand. Researchers have known about some peptides for decades, and dozens have been turned into safe and effective drugs. The hormone insulin is a peptide that moves sugar from the bloodstream into cells; GLP-1, or glucagon-like peptide-1, spurs the pancreas to release insulin and slows the passage of food through the gut. (Peptides are usually defined as having about fifty amino acids or fewer; more than that and they’re proteins.)

https://www.newyorker.com/magazine/2026/04/13/why-are-people...