Glykogeenivarastointihäiriöt

Glykogeenivara (glycogen reserve) refers to the storage form of glucose in animals. Glycogen is a highly branched polymer of glucose connected by alpha-1,4 linkages with alpha-1,6 branches, enabling rapid synthesis and breakdown. In humans, the two major sites are the liver and skeletal muscle. Liver glycogen helps maintain blood glucose during short-term fasting, while muscle glycogen provides a local glucose supply during muscle activity and is not released into the bloodstream.

Amounts vary by body size and activity. An average adult typically stores about 100 grams of glycogen in the liver and roughly 300–600 grams in skeletal muscle, with higher levels in trained individuals. After a meal, hepatic glycogen is replenished; during fasting or prolonged exercise, glycogenolysis increases to supply glucose. Glycogen synthesis (glycogenesis) is promoted by insulin, whereas glycogen breakdown (glycogenolysis) is stimulated by glucagon, epinephrine, and norepinephrine. Regulation involves coordinated signaling and the actions of enzymes such as glycogen synthase, branching enzyme, glycogen phosphorylase, and the debranching enzyme.

Clinical relevance includes glycogen storage diseases (GSDs), genetic disorders affecting glycogen metabolism. Examples include Pompe disease (GSD II), due to lysosomal enzyme deficiency impacting glycogen breakdown; McArdle disease (GSD V), caused by muscle glycogen phosphorylase deficiency; and von Gierke disease (GSD I), due to glucose-6-phosphatase deficiency. Symptoms range from hypoglycemia and hepatomegaly to exercise intolerance, depending on the tissue impact. In health, carbohydrate intake and exercise influence glycogen storage dynamics.