Congenital Hypothyroidism: What is it? Causes, Symptoms, Diagnosis and Treatment

 

Known by its abbreviation as HC, it is inadequate thyroid hormone production in newborns.

It may be due to an anatomical defect in the gland, an inborn error of thyroid metabolism, or iodine deficiency.

It is a pervasive neonatal endocrine disorder, and historically, it was thought that thyroid dysgenesis represented approximately 80% of the cases. However, studies have reported a change in epidemiology, with an incidence of about 1 in 1,500 live births.

It is believed that this is due in part to the increase in congenital hypothyroidism with the thyroid gland in situ.

The lower HC detection cutoffs may also be driving this increase in diagnosis; the altered ethnicities of the population examined, the increase in multiple and premature births, and the iodine status are contributing factors.

Some babies diagnosed with primary congenital hypothyroidism may have temporary disease and no permanent congenital hypothyroidism.

The term endemic cretinism is used to describe groups of children with goiter and hypothyroidism in a defined geographic area. It was discovered that these areas had little iodine and it was determined that the cause of endemic cretinism was iodine deficiency.

 

In 1920, an adequate dietary iodine intake prevented endemic goiter and cretinism. Goiter and endemic cretinism are still observed in some areas, such as the regions of Bangladesh, Chad, China, Indonesia, Nepal, Peru, and Zaire.

The term sporadic cretinism was initially used to describe the random appearance of cretinism in non-endemic areas.

Causes

The cause of these abnormalities was identified as thyroid glands that do not work or that are not working. This replaced the descriptive term sporadic cretinism with the etiological term congenital hypothyroidism.

It was discovered that treatment with thyroid replacement therapy causes some improvement in these babies, although many remained altered. Morbidity due to congenital hypothyroidism can be reduced to a minimum by early diagnosis and treatment.

Although initial preliminary studies were performed with thyroid-stimulating hormone (TSH) levels in umbilical cord blood, mass screening by TSH and thyroxine radioimmunoassay from blood spots on filter paper were obtained for testing, became possible. Of neonatal detection.

Signs and symptoms

Symptoms and signs include the following:

  • Decreased activity
  • Large anterior fontanelle.
  • Poor diet and weight gain.
  • Small stature.
  • Jaundice .
  • Decreased bowel movements or constipation.
  • Hypotonia .
  • Scream hoarse.

Often, affected babies are described as “good babies” because they rarely cry and sleep most of the time. The physical findings of hypothyroidism may or may not be present at birth.

The signs include the following:

  • Thick facial features.
  • Macroglossia.
  • Hernia umbilical.
  • Mottled skin
  • Developmental delay.
  • Pallor.

Anemia can occur due to a lower requirement for oxygen transport. A small but significant number (3-7%) of babies with congenital hypothyroidism have other congenital disabilities, mainly atrial and ventricular septal defects.

Diagnosis

The diagnosis of primary hypothyroidism is confirmed by demonstrating decreased serum thyroid hormone levels (free or free T4) and elevated levels of stimulating thyroid hormone (TSH).

If hypothyroidism mediated by maternal antibodies is suspected, maternal and neonatal antithyroid antibodies can confirm the diagnosis.

These antibodies are a rare cause of congenital hypothyroidism. The combination of serum levels of low or low-normal T4 and a serum TSH within the reference range suggests a deficiency of thyroid-binding globulin (TBG).

This congenital disorder does not cause any pathological consequences, but it must be recognized to avoid the unnecessary administration of thyroid hormone.

Thyroid scan

Exploring the thyroid is not necessary to perform or confirm the diagnosis of congenital hypothyroidism, but it can provide important information about the etiology.

On thyroid examination, the absence of radionuclide uptake suggests sporadic hypothyroidism, but it can also occur when absorption is blocked by excess iodide or thyroid receptor-blocking antibodies.

The thyroid ultrasound may show thyroid tissue if no uptake is found in the isotopic scan.

A thyroid scan may also show the presence of an ectopic thyroid, such as a lingual or sublingual gland, which is also sporadic. A bilobed thyroid in the correct position or a goiter would suggest an inborn error of thyroid hormone production or transient hypothyroidism or hyperterotropinemia.

Other studies of images

Ultrasound may be a reasonable alternative or an addition to the scan but may not reveal some ectopic glands.

A lateral X-ray of the knee can be obtained to look for the distal femoral epiphysis; This ossification center appears around 36 weeks of gestation, and its absence in a term or term newborn indicates prenatal effects of hypothyroidism.

Treatment

The primary pillar in treating congenital hypothyroidism is the early diagnosis and replacement of thyroid hormone. Optimal care can include diagnosis before 10-13 years of age and normalization of blood levels of thyroid hormone at three weeks of age.

Only levothyroxine is recommended for treatment. Parents should be provided with the hormone in a pill and be taught proper administration.

The pills can be crushed in a spoon; dissolved with a small amount of breast milk, water, or other liquid immediately before administration; and administered to the child with a syringe or dropper.

The pills should not be mixed in a bottle full of formula. Young children usually chew the tablets without problems or complaints.

Initial doses of 10-15 mcg per kg per day have been recommended, equivalent to an initial amount of 50 mcg in many newborns. Well-developed developmental outcomes were reported, but with higher stimulating thyroid hormone (TSH) levels, with half this initial dose of 25 mcg per day.