The pancreas produces four main hormones: insulin, glucagon, somatostatin, and pancreatic polypeptide. A fifth hormone, ghrelin, is produced in tiny amounts. These hormones work together to keep your blood sugar stable and regulate appetite, and they’re released directly into your bloodstream from small clusters of cells called the islets of Langerhans.
Two Jobs, One Organ
The pancreas pulls double duty. About 95% of it is dedicated to digestion, producing enzymes that flow through ducts into the small intestine to help break down food. This is the exocrine function.
The remaining portion is the endocrine pancreas, made up of roughly a million tiny cell clusters (the islets of Langerhans) scattered throughout the organ. Each islet contains several types of specialized cells, and each cell type produces a different hormone that gets released straight into the bloodstream. It’s this endocrine side that most people are asking about when they search for pancreatic hormones.
Insulin: The Blood Sugar Lowering Hormone
Insulin is the pancreas’s most well-known product, made by beta cells, which account for about 75% of each islet. Its primary job is pulling glucose out of the bloodstream and into cells where it can be used or stored.
After you eat a meal, your blood sugar rises. Beta cells detect this increase and release insulin in response. High insulin levels drive glucose into muscle, fat, and liver cells. In the liver specifically, insulin promotes the storage of glucose as glycogen, a compact energy reserve your body can tap into later. As long as insulin levels stay elevated, your body is in storage mode.
Between meals and overnight, insulin levels drop. This low-insulin state signals the body to start releasing its stored fuel. The liver breaks down glycogen back into glucose and sends it into the bloodstream to keep your brain and organs supplied. This cycle of storage and release is how your body maintains blood sugar in a normal range, which the American Diabetes Association defines as below 100 mg/dL when fasting. A fasting level between 100 and 125 mg/dL indicates prediabetes, and 126 mg/dL or higher points to diabetes.
When insulin production fails or the body stops responding to it properly, the result is diabetes. In type 1 diabetes, the immune system destroys beta cells, eliminating insulin production almost entirely. In type 2 diabetes, cells gradually become resistant to insulin’s effects, and beta cells eventually can’t keep up with demand. On the rare opposite end, a tumor called an insulinoma causes beta cells to multiply uncontrollably and flood the body with excess insulin, driving blood sugar dangerously low.
Glucagon: The Blood Sugar Raising Hormone
Glucagon does the opposite of insulin. Produced by alpha cells, which make up about 20% of each islet, glucagon raises blood sugar when it drops too low.
Between meals, when glucose from your last meal has been absorbed and blood sugar starts to fall, alpha cells release glucagon. This hormone signals the liver to break down its glycogen stores into glucose and release it into the bloodstream. Glucagon also triggers the liver to produce new glucose from non-sugar sources like amino acids, and to generate ketones, an alternative fuel the brain and muscles can use.
Insulin and glucagon work as a team in constant opposition. During a meal, insulin rises and glucagon falls, shifting the body into storage mode. Between meals, glucagon rises and insulin falls, shifting the body into fuel-release mode. This push-pull relationship is the core mechanism keeping your blood sugar stable around the clock. When glucagon is overproduced, usually from a rare tumor called a glucagonoma, it can cause persistently high blood sugar along with weight loss and a distinctive skin rash.
Somatostatin: The Braking System
Delta cells make up about 4% of each islet and produce somatostatin, a hormone that acts as a brake on the other pancreatic hormones. Somatostatin inhibits the release of both insulin and glucagon, preventing either one from overshooting. Think of it as a referee keeping the insulin-glucagon cycle from swinging too far in either direction.
Somatostatin isn’t unique to the pancreas. It’s also produced in the brain and the gut, where it slows digestion and reduces the release of other hormones like growth hormone. But within the islets, its main role is fine-tuning blood sugar control by dampening hormone output when levels are sufficient.
Pancreatic Polypeptide and Ghrelin
The remaining two hormones play smaller but distinct roles. Pancreatic polypeptide is made by PP cells, which account for roughly 1% of each islet. It’s released after meals and is involved in regulating appetite and the rate of digestion, though its exact mechanisms are less well understood than those of insulin and glucagon.
Ghrelin, widely known as the “hunger hormone,” is primarily produced in the stomach, but a tiny population of epsilon cells in the pancreatic islets (less than 1% of the total) also produces it. Within the pancreas, ghrelin appears to inhibit insulin release and stimulate delta cells to produce more somatostatin. This creates an indirect braking effect on blood sugar regulation. The pancreatic contribution of ghrelin is small compared to what the stomach produces, but it adds another layer of local fine-tuning within the islets.
How the Hormones Work Together
The islets of Langerhans function less like isolated factories and more like tightly coordinated neighborhoods. Beta cells, alpha cells, delta cells, PP cells, and epsilon cells sit close together and constantly influence each other’s output. When beta cells ramp up insulin, the signal simultaneously suppresses glucagon from neighboring alpha cells. When delta cells release somatostatin, it dials down both insulin and glucagon at once. Ghrelin from epsilon cells nudges delta cells to release more somatostatin, adding yet another feedback loop.
This layered system of checks and balances is what keeps blood sugar remarkably stable in a healthy person, typically hovering between about 70 and 100 mg/dL before meals despite wide variation in what and when you eat. The pancreas doesn’t rely on a single hormone to get this right. It relies on a conversation between all of them.