How Does Insulin Work in the Body?
Insulin and glycogen
Insulin is a type of hormone produced by the pancreas (or more specifically, beta cells of the islets of Langerhans). It turns blood glucose into energy, thereby regulating blood sugar levels. The islets of Langerhans (otherwise known as pancreatic islets) are tiny, isolated clusters of special cells found in the pancreas. Apart from insulin, the pancreas is also responsible for the production of another hormone called glucagon. In contrast to insulin, glucagon is synthesized by alpha cells of the islets of Langerhans. Both insulin and glucagon are released directly into the bloodstream. These two hormones work antagonistically to each other, helping to control blood glucose levels. In other words, they work in opposition to each other. Insulin is able to prevent excessive elevation of blood glucose while glucagon prevents blood sugar from getting too low. After a meal, the blood sugar level in the body will rise. This stimulates the insulin release from the pancreas, thereby reducing the amount of glucose in the blood. The mechanism by which insulin acts is fairly straightforward. Once released, insulin promotes cellular uptake of glucose, allowing the muscles and liver to either store it as glycogen or use it as immediate energy. The release of glucagon, on the other hand, is triggered by low blood glucose level (e.g. exercising, fasting or overnight). Having an opposite action, glucagon promotes the muscles and liver to breakdown glycogen into glucose, which is subsequently released into the blood vessel to increase blood glucose level.
What happens when insulin do not work?
The opposing actions of insulin and glucagon is vital to the maintenance of blood glucose level. Without insulin, the body will not be able to store or use glucose for energy. This may lead to the accumulation of glucose in the body, resulting in a dangerously high blood sugar level. If the liver develops resistance to insulin, impaired fasting glucose (IFG) may occur. Similarly, insulin resistance or insufficient insulin production may lead to impaired glucose tolerance (IGT). Apart from that, the lack of insulin (or the lack of the body’s response to it) may also cause diabetes mellitus, a condition characterized by excessively high blood sugar level. There are several types of diabetes, including type I diabetes, type II diabetes and gestational diabetes. Type I diabetes occurs when there is an inadequate insulin production (or none at all) due to the immunological destruction of beta cells. On the other hand, type II diabetes is marked by an inadequate response to insulin. Initially, the pancreas may try to produce more insulin to compensate for this, leading to hyperinsulinemia (higher-than-normal insulin level). Type II diabetes occurs when the extra insulin eventually fails to maintain the normal blood sugar.
What to do if insulin fails to work?
To maintain blood sugar levels, patients with type I diabetes are required to take insulin on a daily basis. Insulin can be administrated via an insulin pump (or more commonly, by injection using an insulin pen or syringe and needle). For type II diabetes patients, the condition can be controlled using oral hypoglycemic agents (e.g. glyburide, glipizide, glimepiride, and metformin). For best results, it is recommended to use the medicine in combination with lifestyle modifications such as dietary change or exercise. As the disease progresses, medication alone may not be able to adequately control blood glucose levels. When this happens, patients may have to resort to injectable insulin for better glycemic control. Diabetes patients should periodically monitor their blood glucose levels.