Congenital Hypothyroidism

What is congenital hypothyroidism?

Congenital Hypothyroidism (CH) is the name for babies born with hypothyroidism due to the thyroid gland being absent or severely deficient.1 If it is not detected and treated early irreversible neurological problems and poor growth can occur.2

Some children may develop primary hypothyroidism after birth rather than CH. This is sometimes called acquired hypothyroidism3 and these children do not experience the irreversible neurological problems due to untreated CH.4

CH is found in around 1 in 4,000 live births5 and it is twice as common in females.6  There is a possibility that it is more prevalent in multiple pregnancies.7

What causes it?

75% of cases of CH may be due to a total or incomplete development of the thyroid, which is not inherited or a failure of pituitary control (TSH is absent).4

10% of cases are due to an enzymic failure in the manufacture of thyroid hormones, (defects in thyroglobulin ), which is usually inherited so there may be a risk to further infants.8

5% of cases are due to hypothalamic-pituitary dysfunction and this type of dysfunction usually causes other disorders such as lack of growth hormone etc. This type of cause may include tumours, arterial blockage and congenital defects.4

10% of cases the hypothyroidism is not permanent as it is due to things such as medications that the mother is taking i.e. carbimazole or maternal antibodies where the hypothyroidism improves after delivery.4

Some patients will also have other congenital defects and in some cases, there are genetic defects that have caused CH.9

Lack of early treatment of congenital hypothyroidism may cause delayed mental development, learning difficulties and poor coordination.

What are the signs and symptoms of congenital hypothyroidism?

The signs and symptoms of congenital hypothyroidism can include: 1, 5, 10

  • sleepiness
  • feeding difficulties
  • constipated
  • dry skin
  • hoarse cry
  • puffy appearance
  • the tongue may appear enlarged and may protrude
  • distended stomach
  • large soft spots on the skull
  • jaundice
  • weak and floppy muscles (hypotonia)

In older children, the signs and symptoms may also include:3, 11

  • slow growth possibly causing short limbs
  • delayed tooth development
  • poor school performance
  • lack of energy
  • dry skin
  • delayed pubertal development

How is it diagnosed?

All babies are screened at birth (the heel prick test)1 for hypothyroidism and 8 other rare but serious diseases.12  If a high TSH is detected the baby will then have this confirmed by a venous test.13

In older children, a TSH and an FT4 test may be done as well as thyroid antibody testing.11

How is it treated?

Early detection means early treatment to ensure that infants do not develop an irreversible neurological disability.

Levothyroxine is given with dosage increases until thyroid function tests return to normal and then testing is done regularly until the infant is two years of age. FT4 should be kept in the upper half of the normal range.4

Prognosis

Children’s growth and mental development should be monitored throughout their childhood.4 As long as they are on the right treatment and dosage, they should remain well.

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Date updated: 22/03/21 (V1.8) Review date: 29/08/21

References

  1. Congenital Hypothyroidism
    https://www.gosh.nhs.uk/conditions-and-treatments/conditions-we-treat/congenital-hypothyroidism
  2. Congenital Hypothyroidism
    https://ghr.nlm.nih.gov/condition/congenital-hypothyroidism#inheritance
  3. Acquired Hypothyroidism in Children
    https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=160&contentid=4
  4. Childhood and Congenital hypothyroidism
    https://patient.info/doctor/childhood-and-congenital-hypothyroidism#ref-1
  5. http://www.swbh.nhs.uk/wp-content/uploads/2012/07/Congenital-hypothyroidism-ML4793.pdf
  6. Park SM, Chatterjee VK; Genetics of congenital hypothyroidism. J Med Genet. 2005 May42(5):379-89.
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1736062/pdf/v042p00379.pdf
  7. Olivieri A, Medda E, De Angelis S, et al; High risk of congenital hypothyroidism in multiple pregnancies. J Clin Endocrinol Metab. 2007 Aug92(8):3141-7. Epub 2007 May
  8. Kumar PG, Anand SS, Sood V, et al; Thyroid dyshormonogenesis. Indian Pediatr. 2005 Dec42(12):1233-5.
  9. PAX8 mutations associated with congenital hypothyroidism caused by thyroid dysgenesis.
    https://www.ncbi.nlm.nih.gov/pubmed/9590296
  10. Congenital Hypothyroidism – What are the signs and symptoms of congenital hypothyroidism?
    https://www.thyroid.org/congenital-hypothyroidism/
  11. Hypothyroidism in Children and Adolescents
    https://www.thyroid.org/hypothyroidism-children-adolescents/
  12. https://www.nhs.uk/conditions/pregnancy-and-baby/newborn-blood-spot-test/
  13. http://www.btf-thyroid.org/information/leaflets/42-congenital-hypothyroidism-guide

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