Congenital hypothyroidism

Congenital hypothyroidism
6 week old female with jaundice due to hypothyroidism.
Specialty	Endocrinology

Congenital hypothyroidism (CH) is

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  3-month-old infant with untreated CH; picture demonstrates hypotonic posture, myxedematous facies, macroglossia, and umbilical hernia
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  Close up of face, showing myxedematous facies, macroglossia, and skin mottling
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  Close up showing abdominal distension and umbilical hernia.
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  Congenital hypothyroidism, copper engraving, 1815

Cause

Around the world, the most common cause of congenital hypothyroidism is

In some instances, hypothyroidism detected by screening may be transient. One common cause of this is the presence of maternal antibodies that temporarily impair thyroid function for several weeks.^[5]

The word "cretinism" is an old term for the state of mental and physical retardation resulting from untreated congenital hypothyroidism, usually due to iodine deficiency from birth because of low iodine levels in the soil and local food sources. The term, like so many other 19th century medical terms, acquired pejorative connotations as it became used in lay speech. It is now deprecated; ICD-10 uses "congenital iodine deficiency syndrome" with additional specifiers for the various types.^{[citation needed]}

Genetics

Congenital hypothyroidism can also occur due to genetic defects of thyroxine or triiodothyronine synthesis within a structurally normal gland. Among specific defects are thyrotropin (TSH) resistance, iodine trapping defect, organification defect, thyroglobulin, and iodotyrosine deiodinase deficiency. In a small proportion of cases of congenital hypothyroidism, the defect is due to a deficiency of thyroid-stimulating hormone, either isolated or as part of congenital hypopituitarism.^[6] Genetic types of nongoitrous congenital hypothyroidism include:

Nongoitrous congenital hypothyroidism has been described as the "most prevalent inborn endocrine disorder".^[7]

Diagnosis

In the developed world, nearly all cases of congenital hypothyroidism are detected by the newborn screening program. These are based on measurement of TSH or thyroxine (T₄) on the second or third day of life (Heel prick).^[1]

Evaluation

If the TSH is high, or the T₄ low, the infant's doctor and parents are called and a referral to a

Prognosis

Most children born with congenital hypothyroidism and correctly treated with thyroxine grow and develop normally in all respects. Even most of those with athyreosis and undetectable T₄ levels at birth develop with normal intelligence, although as a population academic performance tends to be below that of siblings and mild learning problems occur in some.^[9]

Congenital hypothyroidism is the most common preventable cause of intellectual disability. Few treatments in the practice of medicine provide as large a benefit for as small an effort. The developmental quotient (DQ, as per Gesell Developmental Schedules) of children with hypothyroidism at age 24 months that have received treatment within the first 3 weeks of birth is summarised below:^{[citation needed]}

^[10]

Epidemiology

Congenital hypothyroidism (CH) occurs in 1:1300 to 1:4000 births worldwide.