Hypothyroidism is a disorder characterised by low levels of thyroid hormones (T4 and T3). We have covered hypothyroidism more extensively over here. In this document we will cover congenital hypothyroidism.
Causes of hypothyroidism in children
- Congenital hypothyroidism - it is one of the most common endocrine issues that are encountered in neonates. It may be due to thyroid dysgenesis (incomplete or absent thyroid gland development) or thyroid dyshormogenesis (a recessive genetic mutation that results in absence of TPO and improper thyroid hormone synthesis).
- Acquired hypothyroidism
- Autoimmune thyroiditis - more common in the developed world.
- Iodine deficiency - most common in the developing world.
- Total body irradiation for cancer therapy.
Children with chromosomal disorders such a Down syndrome, Turner syndrome, William syndrome are at increased risk of developing hypothyroidism.
⚠️ Risk factors
- Female
- Prematurity
- Low birth weight
- Twins
This is seen in 1 in 2000/4000 babies every year.
Primary congenital hypothyroidism
This is when there is an issue with the thyroid gland itself.
As mentioned previously, it may be due to thryoid dysgenesis or thyroid dyshormogenesis:
- Thyroid dysgenesis (85% of cases) - abnormality with the development affecting the thryoid gland. It may be that it does not develop altogether (agenesis) or that it develops poorly or ectopically (dysgenesis). An ectopic thyroid (thryoid ectopia) occurs when there is a remnant of the thyroid gland found along the pathway of the thyroglossal duct (tongue → neck).
- Thyroid dyshormogenesis (15% of cases) - normal thyroid gland and normal gross anatomical structure. However, there is absence of thyroperoxidase (TPO) enzyme which is key for the production of the hormones. As such, the thyroid hormones do not form.
Secondary congenital hypothyroidism
Similarly to secondary hypothyroidism, this is when there is an issue earlier on in the axis, such as issues with the hypothalamus or pituitary gland that results in low levels of TSH and subsequently low thyroid activation.
😷 Presentation
Most cases are picked up with screening and the babies are asymptomatic at that stage. If it is not picked up early on and the baby becomes symptomatic, some of the features of congenital hypothyroidism in children include:
- Prolonged neonatal jaundice
- Poor feeding
- Constipation
- Increased sleeping
- Reduced activity
- Slow growth and slow development
- Hoarse cry or low cry
- Macroglossia
- Myxoedema
- Enlarged fontanelles
- Hypotonia
- Bradycardia
- Distended abdomen with umblical hernia
- Goitre
🔍 Investigations
⭐️ Congenital hypothyroidism is 1 of the 9 conditions screened for with Guthrie testing (newborn heel prick test),
It is done at 5-8 days old using 4 drops of blood from the baby’s heel which are tested via a special card.
We can otherwise diagnose it using:
- TFTs - raised TSH and low FT4
- Thyroid ultrasound or radionuclide scan - to identify thyroid dysgenesis.
- Auditory assessment - as hypothyroidism may be associated with sensorineural deafness.
🧰 Management
- Levothyroxine
We also need to regularly monitor growth and development of the baby and also monitor their TSH and FT4 levels.
💡 Some children may have transient hypothyroidism in which their hypothyroidism disappears after 2 years old. If there is no definitive cause of the hypothyroidism, we can trial weaning children off at 2-3 years old to see if they produce their own thyroid hormones well enough.