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