Metabolic Disorders

Metabolic disorders are diseases caused by errors in metabolism. The term "metabolism" refers to the sum of the chemical reactions in the body. Metabolic problems can be traced to numerous metabolic pathways found in cells throughout the body.

Metabolic reactions are categorized into two types, anabolic and catabolic. Anabolic reactions construct complex molecules from simple molecules, usually while using up energy that becomes stored in chemical bonds. Catabolic reactions break down complex molecules into multiple simple molecules, usually while releasing energy.

Most metabolic pathways have several chemical steps, each catalyzed by a specific enzyme. Enzymes facilitate a chemical reaction by lowering the amount of energy required to initiate the reaction. Enzymes are so important to normal metabolic functions that the absence of an enzyme can prolong a reaction or prevent it from occurring. The molecules converted by an enzyme are called substrates. When an enzymatic step in a metabolic pathway causes the buildup of these substrates, then the accumulated molecules can be toxic and lead to a metabolic disorder. Some metabolic disorders are barely detectable, whereas others are life-threatening.

Most metabolic disorders are caused by genetic mutations present as inborn errors of metabolism. But some metabolic disorders are caused by dysfunctions of the endocrine system.