Encyclopedia of Health and Medicine

metabolism 227
Doctors commonly refer to genetic-based conditions
as inborn errors of metabolism. Many of
these disorders affect the function of specific
enzymes that facilitate the conversion or storage
of nutrients to energy within the metabolic pathway.
The consequence may affect the body as a
whole or the activity of specific kinds of cells such
as muscle cells or nerve cells (neurons).
Researchers do not know the extent to which
genetic factors influence acquired metabolic conditions
such as hyperthyroidism, hypothyroidism,
and type 2 diabetes.
Symptoms of metabolic disorders vary depending
on how the disorder affects metabolism and
may include
• neurologic deficit and development delays
• CARDIOMYOPATHY
• hearing loss
• vision disturbances
• myoclonus
• seizures
• weakness or movement difficulties
• failure to thrive
Inborn disorders of metabolism may not
become apparent until a child is several months to
several years old, by which time the condition
often causes significant damage to organ systems.
Newborn screening for some such disorders, such
as PKU, is common in the United States and many
other countries. Early detection of PKU and many
other metabolic disorders allows treatment or
management, such as enzyme replacement therapy
or dietary restrictions, to prevent the condition
from causing damage. However, most genetic
disorders of metabolism are not curable at present.
Hormone replacement therapy is the treatment for
hypothyroidism and insulin-dependent diabetes.
Confirming the diagnosis of metabolic disorders
may be as simple as common blood tests, such as
for diabetes or hypothyroidism, or may require
sophisticated laboratory procedures and genetic
(DNA) testing. There are no known methods of
prevention for most metabolic conditions. Lifestyle
factors such as diet and daily exercise can influence,
and often prevent or reduce the severity of,
type 2 diabetes.
DISORDERS OF METABOLISM
acid lipase disease
coenzyme A deficiencies
DIABETES
Fabry disease
G6PD DEFICIENCY
galactosemia
gangliosidoses
Gaucher disease
HEMOCHROMATOSIS
hyperoxaluria
HYPERTHYROIDISM
HYPOTHYROIDISM
lipidoses
metachromatic leukodystrophy
mitochondrial myopathies muscular dystrophies
Niemann-Pick disease OBESITY
oxalosis
PHENYLKETONURIA (PKU)
Tay-Sachs disease
WILSON’S DISEASE
Continuing advances in genetic and molecular
research are allowing scientists to identify gene
mutations that underlie a number previously
poorly understood syndromes with symptoms of
impaired physical and intellectual development.
Researchers are hopeful that new findings will
result in GENE THERAPY approaches to remedy or
prevent the defective metabolic functions.
See also ANABOLIC STEROIDS AND STEROID PRECUR-
SORS; CELL STRUCTURE AND FUNCTION; EXERCISE AND
HEALTH; HORMONE; METABOLIC EQUIVALENT (MET);
NUTRITIONAL NEEDS; VITAMINS AND HEALTH; WEIGHT LOSS
AND WEIGHT MANAGEMENT.