A collection of disorders in which some part of the body's internal chemistry (see METABOLISM and CATABOLISM) is disrupted. Some of these disorders arise from inherited deficiencies in which a specific ENZYME is absent, abnormal, or does not function properly. Other metabolic disorders occur because of malfunctions in the endocrine system (see ENDOCRINE GLANDS). There may be over- or underproduction of a hormone involved in the control of metabolic activities: a prime example is DIABETES MELLITUS – a disorder of sugar metabolism; others include CUSHING'S SYNDROME; hypothyroidism and hyperthyroidism (see THYROID GLAND, DISEASES OF); and insulinoma (an insulin-producing tumour of the PANCREAS). The bones can be affected by metabolic disorders such as osteoporosis, osteomalacia (rickets) and Paget's disease (see under BONE, DISORDERS OF). PORPHYRIAS, HYPERLIPIDAEMIA, HYPERCALCAEMIA and gout are other examples of disordered metabolism.

There are also many rare congenital disorders described as inborn errors of metabolism (see LYSOSOMAL STORAGE DISEASES).