Glycogen storage disorder - Type Ia (GSDIa) is caused when the body is missing an enzyme that is needed by the liver to convert sugar from its storage form (glycogen) to the form that can be used by the body to produce energy (glucose).  People with GSD cannot maintain their blood glucose levels and develop hypoglycemia (low blood sugar) within a few hours after eating.  Treatment for GSD involves providing the body with an outside supply of glucose.  Symptoms of GSD may include seizures, an enlarged liver, slow growth and short stature.