Congenital hypothyroidism is a condition characterised by a loss of thyroid function. It affects approximately one child in 4,000 births, and up to 20% of cases are hereditary. Congenital hypothyroidism may be the result of the thyroid gland developing incorrectly, complete failure of the gland to develop at all, or the result of an enzyme defect which prevents the production of thyroid hormone. Some children have an ectopic thyroid gland, which means that the thyroid gland develops, but in the wrong position. The thyroid gland is usually located in the neck, below the position of the Adam’s apple. Ectopic thyroid glands are commonly small and less active than the normal thyroid gland, and often the function of an ectopic thyroid gland will become progressively worse over time.
The Guthrie Test
The Guthrie Test is a screening test which can detect congenital hypothyroidism, cystic fibrosis, phenylketonuria and several other diseases in the newborn. The Guthrie test is commonly called the heel prick test, because it uses a sample of blood obtained by pricking the newborn’s heel. A small amount of blood is placed onto a card of filter paper, which is sent to the laboratory where a series of tests are performed on the sample. In the case of congenital hypothyroidism, the blood sample is tested for the levels of thyroid stimulating hormone (or TSH), a hormone which signals to the thyroid gland to produce thyroid hormones, as well as the levels of the thyroid hormones themselves. A positive Guthrie test for congenital hypothyroidism will show higher than normal levels of TSH, and levels of thyroid hormone below the normal range. If the Guthrie test is positive, thyroid function tests are also ordered to confirm the diagnosis of congenital hypothyroidism. A thyroid scan may also be performed.
Signs and Symptoms
With the introduction of the Guthrie Screening test, congenital hypothyroidism is generally detected prior to the development of signs and symptoms. If the condition remains undetected, congenital hypothyroidism may present with the following signs and symptoms:
- Cool skin and lower body temperature
- Jaundice (yellow skin and eyes)
- Fatigue and drowsiness
- Poor feeding
- Delayed growth and development
- Dryness of skin and hair
- Large tongue size
- Excessive crying
Consequences and Treatment
If untreated, congenital hypothyroidism can have serious consequences. Of note, untreated congenital hypothyroidism may result in permanent intellectual disability, growth and developmental delay and effects on the nervous system. However, with the advent of the Guthrie test, the majority of cases of congenital hypothyroidism are detected early and treatment is initiated immediately to prevent the complications of the disorder.
The aim of treatment for congenital hypothyroidism is to give the child the thyroid hormones their thyroid gland is unable to produce. The hormone which is replaced is called thyroxine, and it is generally given in the form of a tablet. It is important that thyroxine tablets are taken regularly and that the levels of thyroxine in the blood are monitored regularly to ensure that the right dosage is being administered to prevent the symptoms and consequences of the condition. In most patients, long-term treatment with thyroxine provides excellent results.