Glucose is a large energy source for the body. It is stored by the body in the form of glycogen and released into the blood as needed with the help of special proteins called enzymes.

There are different types of GSD but all people who have GSD are born with the disease. When a person has GSD:

  • The liver cannot control the use of glycogen and glucose because certain enzymes are missing that control the change of sugar (glucose) into its storage form (glycogen) or release of glucose from glycogen.  
  • An abnormal amount of glycogen is stored in the liver.
  • Not enough glucose is in the blood (also called hypoglycemia). 

Many sugars (including glucose) are found in foods and are used by the body as a source of energy. After a meal, blood glucose levels rise. The body stores the extra glucose that is not needed right away as glycogen in the liver and muscles. Later, as the blood glucose levels in the body begin to drop, the body uses this stored energy.

These sugars, stored in the form of glycogen, need to be processed by enzymes in the body before they can carry out their functions. If the enzymes needed to process them are missing, the glycogen or one of its related starches can build up in the liver, causing problems.