The pancreas and its hormones

Pancreas is a short word for an organ with a big role: it helps digest food and keeps blood sugar under control. Here, we explain which hormones the pancreas produces, what they do and why they matter for your workouts and appetite.

The pancreas: why this organ matters

The pancreas lies behind the stomach, against the back wall of the abdominal cavity. The original text describes it as a relatively large organ, approximately 15 cm long and weighing 80 100 g. Most of the organ functions as a gland that produces digestive juices. Only a small proportion of its cells, around 1–2%, produce hormones.

These hormone-producing cells are found in small clusters known as the islets of Langerhans. They are classified as A or a cells, B or b cells and D or D cells. Their distribution is fairly clear: A cells account for 20–25%, B cells for 60–75% and D cells for 5–15% of all endocrine cells.

Why does this matter to you as a fitness.ee reader? Because blood sugar, hunger, energy for training and recovery depend on more than what you eat or your training program. Hormones are working behind the scenes. When these signals are out of balance, you quickly feel the effects: your energy fluctuates, your appetite changes and it becomes harder to sustain a consistent effort during workouts.

The pancreas: insulin, glucagon and somatostatin

Glucagon is produced by the A cells in the islets of Langerhans. It acts primarily on the liver. When blood sugar falls or your body needs extra energy, glucagon helps the liver break down glycogen and release glucose into the bloodstream. Put simply, glucagon raises blood sugar when your body needs it.

Glucagon also promotes gluconeogenesis, particularly from amino acids. This means your body can make glucose from other starting materials when needed. Glucagon also affects fatty acid metabolism in the liver and may increase ketone body production. In fat tissue, it promotes lipolysis, the breakdown of fat, although the practical significance of this is generally smaller than that of its effects on the liver.

Insulin is synthesized by B cells. Its best-known role is lowering blood sugar. It helps glucose enter cells, promotes glycogen storage in the liver and muscles, and inhibits processes that would raise blood sugar too much. When you eat a meal containing carbohydrates, insulin is among the main hormones that help your body take up the energy it provides.

An important detail for training is that working muscle can use glucose even when insulin levels are very low. At rest, glucose uptake by muscle cells depends more heavily on insulin. Nerve cells and red blood cells, however, use glucose independently of insulin, as glucose is almost their only energy source.

Insulin also affects fat and protein metabolism. It promotes the storage of fatty acids as triglycerides and inhibits lipolysis by reducing lipase activity. In protein metabolism, insulin has an anabolic effect: it helps amino acids enter cells and supports protein synthesis. It is no surprise that its effects are often compared with those of growth hormone.

Somatostatin is produced by D cells. Its role is mainly inhibitory: it acts on A and B cells to reduce the synthesis and secretion of glucagon and insulin, respectively. Somatostatin is also produced in the hypothalamus, where it acts as a signal that inhibits growth hormone release.

The pancreas and blood sugar regulation

Among the pancreas’s most important functions is keeping blood sugar as stable as possible. When plasma glucose levels rise, insulin secretion increases. When glucose levels fall, insulin secretion slows. Glucagon works in the opposite way: rising blood sugar inhibits its production, while falling blood sugar stimulates it.

So what actually happens after a meal? Higher levels of glucose and amino acids in the blood activate B cells. Protein-rich food can also stimulate A cells at the same time, so insulin and glucagon levels may rise together. This effect may not be particularly strong, but it can last longer.

In this situation, insulin helps move amino acids from the blood into tissue cells and supports protein synthesis. Glucagon helps the liver use amino acids in gluconeogenesis. Your body does this for a reason: it is trying to keep energy available while building and repairing tissues.

Other hormones also influence insulin. Somatostatin, epinephrine and norepinephrine inhibit insulin secretion. Gastrin, secretin and cholecystokinin, which are produced in the digestive tract, stimulate B-cell activity. Glucagon secretion is promoted mainly by catecholamines, while somatostatin and insulin inhibit it.

The pancreas: what it means for your training

If you train, this does not mean you need to monitor every hormone individually. It is more useful to understand the overall picture. If you eat very irregularly, get little sleep and add a hard workout on top, your hunger and energy levels can fluctuate. Your pancreas responds alongside your nervous system and other hormones.

The autonomic nervous system also plays a role. Increased parasympathetic activity stimulates insulin secretion by the beta cells in the islets of Langerhans, while increased sympathetic activity inhibits it. In glucagon-producing cells, the effect is reversed: parasympathetic signals inhibit secretion, while sympathetic signals stimulate it.

However, the animal studies mentioned in the original text suggest that nervous system control is not the main factor compared with the direct effect of glucose. Even complete denervation of the pancreas does not cause major disturbances in blood glucose levels. The most important signal therefore remains what is happening to glucose and nutrients in the blood.

In practice, this means making simple choices: eat at reasonably regular intervals, combine carbohydrates and protein sensibly, and do not rely solely on coffee and chance to meet your energy needs throughout the day. If you are constantly hungry, unusually thirsty or have a blood sugar problem identified by a doctor, this is no time to experiment. You should speak to your family doctor or an endocrinologist.

FAQ

Does the pancreas only produce hormones?

No. Most of the pancreas produces digestive juices. Only a small proportion of its cells produce hormones, but their effect on blood sugar and metabolism is substantial.

In simple terms, what does insulin do?

Insulin helps lower blood glucose levels and move glucose into cells. It also supports glycogen storage and protein synthesis.

Why is glucagon necessary?

Glucagon helps raise blood sugar when your body needs extra energy. It acts particularly on the liver, where glycogen is converted back into glucose and released into the blood.

Author: Marek Morozov

Source: WHO – physical activity.

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