Thyroid Dyshormonogenesis
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Thyroid dyshormonogenesis is a rare condition due to genetic defects in the synthesis of
thyroid hormones File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones T3 and T4 rect 376 268 820 433 Thyroid-stimulating hormone rect 411 200 849 266 Thyrotropin-releasing hormone rect 297 168 502 200 Hypothalamus rect 66 216 386 ...
. It is due to either deficiency of thyroid enzymes, inability to concentrate, or ineffective binding.


Signs and symptoms

The symtptoms of this disease are: Very Frequent * Decreased circulating thyroxine level * Elevated circulating TSH concentration Frequent * Abnormality of epiphysis * Congenital hypothyroidism * Constipation * Delayed closure of the cranial suture. * Delay of proximal femoral epiphyseal ossification * Feeding difficulties * Goitre * Big posterior fontanelle * Neurodevelopmental problems * Neonatal jaundice * Umbilical hernia Occasional * Abnormality of circulating thyroglobulin concentration * Slow heart rate * Saddle nose deformity * Edema of face * Decreased reflexes * Hypotonia * Hypothermia * Increase of radioactive iodine uptake * Mental handicap * Large tongue * Neonatal hyperbilirubinemia Very Rare * Sensorineural hearing loss


Cause

This is due to inability to produce thyroid hormones due to congenital absence of peroxidase or dehalogenase enzymes


Types

One particular familial form is associated with
sensorineural deafness Sensorineural hearing loss (SNHL) is a type of hearing loss in which the root cause lies in the inner ear, sensory organ (cochlea and associated structures), or the vestibulocochlear nerve (Cranial nerves, cranial nerve VIII). SNHL accounts for a ...
( Pendred's syndrome).
OMIM Online Mendelian Inheritance in Man (OMIM) is a continuously updated catalog of human genes and genetic disorders and traits, with a particular focus on the gene-phenotype relationship. , approximately 9,000 of the over 25,000 entries in OMIM ...
includes the following:


Diagnosis

Diagnosis can be made by elevated serum TSH level and low T4 or free T4 level.  Thyroid dyshormonogenesis diagnosis is based on high radioactive iodine (RAI) uptake of the thyroid gland followed by more than 90% release after sodium perchlorate administration. Thyroid dyshormonogenesis is diagnosed with a 50%-90% release after perchlorate administration, which can be confirmed by genetic testing.


Treatment

Levothyroxine Levothyroxine, also known as -thyroxine, is a synthetic form of the thyroid hormone thyroxine (T4). It is used to treat thyroid hormone deficiency (hypothyroidism), including a severe form known as myxedema coma. It may also be used to tre ...
is the treatment of choice (starting dose 10-15 mcg/kg/day), with the immediate goal of raising the serum T4 level above 130 nmol/L (10 ug/dL) as quickly as possible; with these doses, serum TSH usually normalizes within 2–4 weeks. Frequent laboratory monitoring in infancy is essential to make sure of optimal neurocognitive outcome. Serum TSH and T4 should be measured every 1–2 months in the first 6 months of life, every 3 months between 6 months and 3 years of age, and 4 weeks after any dose change.


References


External links

Thyroid disease Membrane transport protein disorders Congenital disorders of endocrine system {{endocrine-disease-stub