The pancreas is a small organ found near the stomach that has two main roles in the body:
- Endocrine role - this means that it releases hormones into the bloodstream, in this case beta-cells release insulin (which lowers blood glucose) and alpha-cells release glucagon (which raises blood glucose by releasing it from stores).
- Exocrine role - this means that it releases enzymes via a duct into the small intestine for digestion of fats and proteins. This shouldn’t affect hyperinsulinism patients unless they have a near-total pancreatectomy, in which case they will need to take enzyme-replacements with their meals.
In hyperinsulinism the endocrine function, specifically the beta-cells are affected.
In the focal form of the disease the affected cells are located together in a cluster. This focus is generally spherical between 2-10mm but can be much bigger or even have an “octopus” shape. If the focus is removed this should cure the hyperinsulinism.
In the diffuse form all the beta cells in the pancreas are affected. Therefore treatment aims to stop all of these cells producing too much insulin. This is done through medication. If this fails then doctors may decide to remove most of the pancreas. However this does not remove all the beta cells and the hyperinsulinism may persist.
The Release of Insulin
The mechanisms involved in the release of insulin are quite complicated:
- Glucose in the bloodstream moves into the beta cells
- During a series of processes in respiration (glycolysis, Krebs cycle, ETC) this increases the production of ATP
- Increased ATP causes the KATP channel to close
- K+ (potassium ions) build up inside the cell. This causes depolarisation - more positive ions inside than usual.
- Depolarisation causes Ca2+ channels to open
- Ca2+ (calcium ions) enter cell
- Initiates exocytosis where vesicles (small balls) containing insulin bind with the cell surface membrane and insulin is released.
The key thing here is that insulin should only be released if glucose is entering the cell (step 1). There are a number of reasons why insulin might be released when glucose has not entered. Some of those are unknown and others can be explained by genetics. The reason for the insulin release will determine the medication that works for the child.
