The pancreas secretes several hormones, but the two most important are insulin and glucagon. These work in opposite directions to keep your blood sugar stable. The pancreas also produces at least three other hormones from specialized cell clusters called the islets of Langerhans, each playing a supporting role in metabolism and digestion.
Insulin: The Blood Sugar Lowering Hormone
Insulin is the pancreas’s most well-known hormone, produced by beta cells that make up roughly 62% of the cells in each islet. Its primary job is lowering blood sugar after you eat. When glucose enters your bloodstream from a meal, beta cells detect the rise and release insulin in response.
Insulin acts on three main tissues. In skeletal muscle (the body’s largest reservoir of stored carbohydrate and protein), insulin drives glucose and amino acids into cells so they can be used for energy or stored for later. In the liver, insulin signals cells to pull glucose out of the blood and store it as glycogen. In fat tissue, insulin promotes fat storage and blocks the breakdown of existing fat reserves. The net effect is a steady drop in blood sugar back to its normal range.
The release mechanism is tightly controlled. When glucose enters a beta cell, it gets metabolized to produce energy molecules that ultimately trigger the cell to push pre-made packets of insulin out into the bloodstream. This process happens in pulses, ramping up as blood sugar climbs and tapering off as it falls. When this system fails, either because beta cells are destroyed (type 1 diabetes) or because tissues stop responding to insulin properly (type 2 diabetes), blood sugar stays chronically elevated.
Glucagon: The Blood Sugar Raising Hormone
Glucagon does the opposite of insulin. Produced by alpha cells, which account for about 27.5% of islet cells, glucagon raises blood sugar when levels drop too low, such as between meals or during prolonged fasting.
It works primarily through the liver in three ways. First, glucagon signals the liver to break down its stored glycogen back into glucose and release it into the bloodstream. Second, it prevents the liver from absorbing and storing glucose, keeping more of it circulating. Third, during extended fasting when glycogen stores run low, glucagon triggers the liver to build brand-new glucose molecules from non-carbohydrate sources like amino acids, fats, and proteins.
Together, insulin and glucagon form a feedback loop. After a meal, insulin dominates, pulling sugar out of the blood. Between meals, glucagon takes over, pushing sugar back in. This back-and-forth keeps blood glucose within a narrow, safe range around the clock.
Somatostatin: The Regulatory Brake
Delta cells make up about 12% of each islet and produce somatostatin, a hormone that acts as a local brake on both insulin and glucagon. Rather than entering the broader bloodstream to affect distant organs, somatostatin works right inside the islet, diffusing to neighboring cells and dialing down their output.
It uses different pathways depending on the target. Somatostatin suppresses glucagon release from nearby alpha cells through one type of receptor, and inhibits insulin release from beta cells through a different receptor type. This paracrine (cell-to-neighbor-cell) action helps prevent the pancreas from overproducing either hormone, fine-tuning the insulin-glucagon balance rather than letting it swing too far in either direction.
Pancreatic Polypeptide: The Digestive Regulator
After a meal, specialized cells in the islets release pancreatic polypeptide, a hormone focused on digestion rather than blood sugar. Its main role is slowing down the pancreas’s own digestive enzyme secretions. It does this indirectly by acting on receptors in the brain, which then reduces nerve signals traveling back to the pancreas.
Pancreatic polypeptide also relaxes the gallbladder, reducing the pressure that drives bile into the intestine. The overall effect is a modulating influence on digestion, preventing the system from overreacting to food intake.
Ghrelin: The Rare Fifth Hormone
A small population of epsilon cells in the pancreas produces ghrelin, the same “hunger hormone” secreted in larger quantities by the stomach. During fetal development, epsilon cells account for roughly 10% of islet cells and likely contribute meaningfully to circulating ghrelin levels. In adults, however, they shrink to less than 1% of islet cells, making them extremely rare. Single-cell analysis of nearly 15,000 human islet cells identified just 11 epsilon cells, a frequency of 0.08%. While the stomach remains the body’s primary ghrelin source, the pancreatic contribution during early development suggests these cells play a role in metabolic programming before birth.
How These Hormones Work Together
The pancreas isn’t just producing five independent hormones. The physical layout of the islets matters. Alpha, beta, and delta cells sit in close proximity, allowing somatostatin to reach its targets almost instantly without relying on the bloodstream. This architecture means the islet functions as a miniature organ, with internal feedback loops adjusting hormone output moment to moment.
Blood sugar control depends on the ratio between insulin and glucagon more than the absolute amount of either one. Somatostatin modulates both sides of that ratio. Pancreatic polypeptide and ghrelin operate on longer timescales, influencing digestion and appetite. The result is a layered system where each hormone checks or complements the others, keeping metabolism stable across meals, fasting, exercise, and sleep.