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Insulin is a hormone that helps regulate the amount of sugar in your blood. It's produced in many different living things and is part of a group of hormones that help keep your body in balance. These hormones are made in glands in your body and travel to different organs to tell them what to do. Insulin's job is to lower the amount of sugar in your blood when it gets too high. This happens when you eat sugary foods or don't exercise enough. Insulin helps store the extra sugar in your body so it doesn't cause problems. If your body doesn't produce enough insulin or it doesn't work properly, it can lead to conditions like diabetes or PCOS. These conditions can cause high blood sugar, which can be dangerous if left untreated. If you want to learn more about how hormones like insulin work to keep your body healthy, check out our article on the Endocrine System!

What is Insulin?

Insulin is a hormone that helps regulate the amount of sugar in your blood. It works with another hormone called glucagon to keep your blood sugar levels in check. The two hormones work together in a way that keeps your blood sugar levels within a certain range. Insulin is produced by the pancreas when your blood sugar levels get too high. It helps your muscles, liver, and fat cells absorb sugar from your blood, which lowers your blood sugar levels. This process helps maintain a steady balance in your body called homeostasis. Homeostasis is when your body keeps everything in balance to stay healthy. Negative feedback is a process that helps your body regulate itself. It's a way for your body to reverse changes and keep things at a steady state. To learn more about negative feedback and how it helps your body stay healthy, check out our article on Negative Feedback!

Insulin and Blood Glucose Homeostasis

Insulin is believed to have existed as far back as the first eukaryotic organisms and is now produced by virtually all vertebrate organisms, and many invertebrate organisms. The structure of this protein is so conserved that insulin from many species is effective in regulating human blood sugar levels albeit with mildly varying degrees of efficacy.

Insulin Function:

Insulin is a hormone in your body that helps control your blood sugar levels. It does this by triggering a series of chemical reactions that remove sugar from your blood and store it for later use. When pancreas detects of sugar in your blood, it releases insulin. Insulin binds to receptors on the surface of fat, muscle, and liver cells, which causes glucose to be removed from your blood and stored in different ways. In the short term, glucose is stored as glycogen in liver and muscle cells. Glycogen is a type of glucose polymer that's stored in dense granules within the cell. Insulin helps form glycogen by triggering a series of reactions that create chains of glucose molecules. These chains are then elongated and branched to form the glycogen granule. For long-term storage, insulin acts on fat cells to trigger the uptake of glucose and its conversion to fatty acids. The combined action of glycogen and fatty acid synthesis lowers your blood sugar levels back towards the ideal range. Insulin also increases the rate of glucose consumption, which helps lower blood sugar levels even further. To learn more about how your body controls blood sugar levels, check out our article on the Control of Blood Glucose Concentration!

Insulin Production:

Insulin is primarily produced in the beta cells of the pancreas, which are located in the islets of Langerhans. These cells are responsible for producing and secreting insulin in response to changes in blood glucose levels. The islets of Langerhans are clusters of cells in the pancreas that are composed of several different types of cells, including alpha, beta, delta, gamma, and epsilon cells. The alpha cells produce glucagon, while the beta cells produce insulin. The other cells produce different that are involved in regulating digestion and other metabolic processes.

Insulin can also be produced artificially using genetic engineering techniques. By extracting the insulin gene from human DNA and inserting it into yeast or bacteria, scientists can produce large amounts of insulin that are identical to human insulin. This method of insulin production is much more efficient than extracting insulin from animals, which was the primary method used before genetic engineering became widely available.

The insulin gene is transcribed into mRNA, which is then translated into a protein called preproinsulin. This protein undergoes several stages of post-translational modifications before it becomes insulin. First, a signal sequence is removed in the rough endoplasmic reticulum, forming proinsulin. Further cleavage then results in three smaller peptides held together with disulfide bonds, along with a small connecting structure known as c-peptide. The Golgi apparatus then packages this proinsulin into insulin vesicles, which cut out the c-peptide, forming the final secreted product, insulin.

In summary, insulin is primarily produced in the beta cells of the pancreas, and it is involved in regulating blood glucose levels. Insulin can also be produced artificially using genetic engineering techniques, which is a more efficient method than extracting insulin from animals. The insulin gene is transcribed mRNA, which is then translated into preproinsulin, and undergoes several modifications before it becomes insulin.

Insulin Secretion

After insulin is synthesized and packaged into vesicles, these vesicles are stored within the beta cells of the pancreas until they are needed. When blood glucose levels rise, glucose enters the beta cells and is converted to ATP through a series of reactions. The ATP then closes normally open potassium channels in the cell membrane, which causes a change in the charge of the cell membrane. This change in charge opens calcium channels, allowing calcium ions to enter the cell. The increase in calcium ions triggers the fusion of the insulin vesicles with the cell membrane, releasing insulin into the bloodstream through a process called exocytosis.

This process is tightly regulated and occurs only when blood glucose levels are high enough to warrant insulin release. As blood glucose levels begin to decrease, the production of ATP decreases, and the potassium channels in the cell membrane begin to open again. This causes the membrane charge to return to its resting state, and the calcium channels close, slowing the release of insulin. Once blood glucose levels have returned to normal, insulin release stops completely. This tight regulation is critical for maintaining normal blood glucose levels and preventing hypoglycemia.

In summary, insulin release from beta cells is triggered by an increase in blood glucose levels. Glucose enters the beta cells and is converted to ATP, which triggers the release of insulin through a process called exocytosis. This process is tightly regulated and stops once blood glucose levels have returned to normal. This is important for maintaining normal blood glucose levels and preventing hypoglycemia.

Insulin Structure

Insulin before undergoing its post-translational modifications is a 110 amine residue long protein. However, following the removal of various sections, its secreted form is 51 residues long. Before being secreted, insulin is stored in bundles of six within the granule, however, this splits into the active form of single units upon being released from the beta cells.

Insulin Diseases

Insulin is involved in many diseases that affect humans, stemming from either changes in the body's response to insulin or changes in the production of insulin. These diseases include: Insulin Resistance Syndrome Diabetes Insulinoma PCOS

Insulin Resistance Syndrome and Symptoms

Insulin resistance syndrome, also known as metabolic syndrome, is a condition that is commonly seen as a precursor to type 2 diabetes. However, it has also been linked to a range of other diseases, including hypertension, hyperlipidemia, fatty liver disease, and atherosclerosis. The exact mechanisms behind insulin resistance syndrome and its links to these diseases are not fully understood, but it is believed that consistently elevated blood sugar levels result in an overproduction of insulin. Over time, the cells in the body, particularly liver, fat, and muscle cells, become resistant to or ignore the signals of insulin, requiring larger and larger amounts to be released in order for the same drop in blood glucose levels to occur.

Many factors in modern lifestyles can increase the risk of insulin resistance syndrome occurring, including stress, obesity, a sedentary lifestyle, and aging. This means that dietary and exercise changes can be an effective preventative measure, significantly lowering the chances of developing this syndrome. Presently, treatment for insulin resistance syndrome mainly centers around lifestyle changes, such as increasing physical activity and adopting a healthy diet, along with treating the resultant disorders, rather than curing the insulin resistance itself.

It is important to note that insulin resistance syndrome is a complex condition with a range of potential causes and impacts, and that its effects can vary widely from person to person. However, by understanding the underlying mechanisms of this syndrome and taking steps to prevent or manage it, individuals can reduce their risk of type  diabetes other associated diseases, and improve their overall health and wellbeing.


Diabetes is a broad term for a variety of conditions that all center around consistently elevated blood glucose levels. The two main types of diabetes are type 1 and type 2. In type 1 diabetes, the immune system attacks the beta cells in the pancreas, leading to a decrease or complete cessation of insulin production. In type 2 diabetes, the cells become resistant to insulin, resulting in consistently elevated blood glucose levels. Treatment varies between the two types, with insulin always being necessary for type 1, while type 2 can often be managed through lifestyle changes such as exercise and healthy eating, combined with oral antidiabetic medications.

Both types of diabetes can lead to many complications, mainly stemming from blood vessel damage caused by consistently elevated blood glucose levels. This damage can increase the risk of cardiovascular conditions such as stroke, coronary artery disease, and peripheral artery disease. Damage to smaller blood vessels, such as capillaries, can also cause a range of diseases such as diabetic retinopathy, nephropathy, and neuropathy.

In the UK alone, diabetes is responsible for 530 heart attacks and 680 strokes every week, making these complications the leading cause of death in people with diabetes. It is important for individuals with diabetes to manage their blood glucose levels and work closely with their healthcare providers to prevent and treat any potential complications.


An insulinoma is a type of tumor that forms in the pancreas from beta cells, which are responsible for secreting insulin into the bloodstream. The symptoms of insulinoma stem from the fact that the tumor's insulin secretion is dysregulated and does not respond properly to changes in insulin levels. This can result in excessively low blood glucose levels, a condition known as hypoglycemia. Symptoms of hypoglycemia can include confusion, dizziness, headaches, sweating, weakness, seizures, and loss of consciousness. In severe cases, hypoglycemia can life-threatening.

Treatment for insulinoma usually involves surgical removal of the tumor. In some cases, medication may be used to help regulate blood glucose levels before and after surgery. After surgery, blood sugar levels typically return to normal, and symptoms of hypoglycemia subside. In rare cases, the tumor may be cancerous, and additional treatment may be necessary.

It is important to note that while insulinomas are rare, they can cause significant health problems if left untreated. Early diagnosis and treatment are crucial for managing symptoms and preventing complications. Individuals who experience symptoms of hypoglycemia, particularly if they occur regularly, should seek medical attention to determine the underlying cause and receive appropriate treatment.


PCOS or polycystic ovary syndrome is a syndrome in which a woman's hormone levels are disordered, resulting in the production of excessive levels of male hormones. It is characterised by difficulty becoming pregnant, skipped menstruations, excess hair growth, cramps and many other conditions. PCOS can stem from insulin resistance, with heightened levels of insulin causing increased ovarian testosterone production.

Insulin - Key takeaways Insulin is a protein hormone produced by beta cells in the pancreas. It lowers blood sugar levels by increasing glucose uptake by muscles, the liver and adipose cells. Insulin production and secretion are a key part of Blood Glucose Homeostasis. It is involved in an array of diseases including diabetes, PCOS and insulinoma.


what is insulin?

Insulin is a protein hormone produced in the pancreas, which lowers blood sugar levels. 

where is insulin produced?

Insulin is produced in the beta-cells located within the islets of Langerhans in the pancreas. 

what does insulin do?

Insulin lowers blood sugar levels by triggering increased glucose uptake by the liver, adipocytes and muscles. 

What is the structure and function of insulin? 

Insulin is a 51 residue long protein, stored in bundles of six before splitting into single units after secretion. Its function is to trigger increased uptake of glucose from the blood by the liver, muscles and adipocytes. 

How much insulin does the pancreas produce? 

The pancreas has at any given time around 200 units of insulin and secretes on average 30-50 units daily.

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