SLC16A2
Encyclopedia
Monocarboxylate transporter 8 (MCT8) is a protein
that in humans is encoded by the SLC16A2 gene
.
s including the thyroid hormones T3
and T4
.
/floppy infants with delayed milestones). This genetic defect was known as Allan-Herndon-Dudley syndrome
(since 1944) without knowing its actual cause. Some of the symptoms for this disorder as are follows: normal to slightly elevated TSH
, elevated T3 and reduced T4 (ratio of T3/T4 is about double its normal value). Normal looking at birth and for the first few years, hypotonic (floppy), in particular difficulty to hold the head, possibly difficulty to thrive, possibly with delayed myelination (if so, some cases are reported with an MRI pattern similar to Pelizaeus-Merzbacher disease
, known as PMD), possibly with decreased mitochondrial enzyme activities, possibly with fluctuating lactate
level. Patients have an alert face, a limited IQ, patients may never talk/walk, 50% need feeding tube, patients have a normal life span. This disease can be ruled out with a simple TSH/T4/T3 thyroid test.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
that in humans is encoded by the SLC16A2 gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
.
Function
MCT8 transports a variety of iodo-thyronineThyronine
Thyronine is a deiodinated form of thyroxine....
s including the thyroid hormones T3
Triiodothyronine
Triiodothyronine, C15H12I3NO4, also known as T3, is a thyroid hormone. It affects almost every physiological process in the body, including growth and development, metabolism, body temperature, and heart rate....
and T4
Thyroxine
Thyroxine, or 3,5,3',5'-tetraiodothyronine , a form of thyroid hormones, is the major hormone secreted by the follicular cells of the thyroid gland.-Synthesis and regulation:...
.
Clinical significance
A genetic disorder (discovered in 2003 and 2004) is caused by mutation in the transporter of thyroid hormone, MCT8, also known as SLC16A2, is believed to be account for a significant fraction of the undiagnosed neurological disorders (usually resulting in hypotonicHypotonia
Hypotonia is a state of low muscle tone , often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases and disorders that affect motor nerve control by the brain or muscle strength...
/floppy infants with delayed milestones). This genetic defect was known as Allan-Herndon-Dudley syndrome
Allan-Herndon-Dudley syndrome
Allan–Herndon–Dudley syndrome is a rare disorder of brain development that causes moderate to severe mental retardation and problems with movement. This condition, which occurs almost exclusively in males, disrupts development from before birth....
(since 1944) without knowing its actual cause. Some of the symptoms for this disorder as are follows: normal to slightly elevated TSH
Thyroid-stimulating hormone
Thyrotrophin-stimulating hormone is a peptide hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid gland.- Physiology :...
, elevated T3 and reduced T4 (ratio of T3/T4 is about double its normal value). Normal looking at birth and for the first few years, hypotonic (floppy), in particular difficulty to hold the head, possibly difficulty to thrive, possibly with delayed myelination (if so, some cases are reported with an MRI pattern similar to Pelizaeus-Merzbacher disease
Pelizaeus-Merzbacher disease
Pelizaeus–Merzbacher disease is a rare central nervous system disorder in which coordination, motor abilities, and intellectual function are delayed to variable extents.-Classification:...
, known as PMD), possibly with decreased mitochondrial enzyme activities, possibly with fluctuating lactate
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
level. Patients have an alert face, a limited IQ, patients may never talk/walk, 50% need feeding tube, patients have a normal life span. This disease can be ruled out with a simple TSH/T4/T3 thyroid test.