| What is congenital hypothyroidism?
The heel prick or Guthrie, test, where a small amount of blood is collected from your baby's foot a few days after birth, checks for thyroid function among other rare conditions. Dr Howard Lee explains how early detection can allow a child to develop normally What is congenital hypothyroidism? Congenital hypothyroidism affects infants from birth (congenital) and results from the loss of thyroid gland function (hypothyroidism). Untreated, it's a threat to physical and mental development. It is a fairly common childhood endocrine disorder that in the UK affects 1 in every 3,500 to 4,000 infants. The condition is twice as common in girls. The thyroid gland either fails to develop properly before birth - or fails to work adequately immediately afterwards, and this is the commonest cause of the disease.
Serious long-term effects If your baby does have hypothyroidism, it is vital that an early diagnosis is made. Early treatment is imperative in order to prevent irreversible damage - which causes severe mental retardation - occurring to the nervous system. The absence of thyroid hormones can cause very serious mental and physical retardation - cretinism and dwarfism are long-term effects that occur if the condition is not spotted. Untreated disease can present as a floppy infant, with stunted growth - perhaps the first suggestions being failure to meet the usual growth milestones - and there is often poor feeding. There may also be problems with constipation and jaundice. Changes in the appearance of the baby are also characteristic: the skin is pale and thicker; the baby's face may be dull, slow-reacting and slightly puffy; the tongue may be more prominent in an open mouth. The infant will seem floppy, because the muscle tone is decreased, and tend to sleep excessively. What is the thyroid gland? The thyroid is a small, bow tie shaped gland, sitting in front of the neck just below the Adam's apple. It produces a hormone that plays an important part in regulating the body's metabolism and organ function, and it influences every organ, tissue and cell in the body. The thyroid hormone, thyroxine/T4, is in turn produced under stimulation from the thyroid-stimulating hormone/TSH - generated by the pituitary gland at the base of the brain. How is the condition diagnosed? Babies are screened in the first days of life for a variety of conditions. The heel prick or Guthrie test (where a small drop of blood is taken for testing) is usually performed by the midwife in the first 24 to 72 hours after birth. Since the early 1980s thyroid screening has been included within this test. The lab can identify either a low thyroxine/T4 level - or a high thyroid stimulating hormone/TSH level (presence of either can indicate a poorly functioning thyroid gland). Screening tests can sometimes be confusing, and infantile hypothyroidism can still develop even when the test is normal. In these cases, there may be a repeat test, using a small sample of vein blood. Sometimes your doctor will order X-rays of the baby's legs to show the bone ends at the knee joints. These can show immature appearances in babies who have hypothyroidism, and helps to confirm a diagnosis. Are there any obvious signs of congenital hypothyroidism? Infants with this thyroid gland abnormality will either appear to be quite normal at birth or will have such subtle features that the new parents won't be aware of a potentially serious problem. Certain factors could indicate a possibility of hypothyroidism, and these will be taken into account during the clinical assessment by health care workers:
What checks and treatments are available? In a proven case of congenital hypothyroidism - whatever the cause is thought to be - the treatment is the same. It is safe, simple and effective, and involves replacing the missing thyroid hormone. Thyroxine is taken in pill form daily for life. The correct dosage is determined by making regular estimations of the thyroid hormones present in the blood, to keep the thyroxine/T4 concentration within the normal range. This will be especially important in the first few years of life. Frequent visits to the doctor will be necessary but these, as well as the blood tests, will become fewer once the baby's condition is brought under control. Generally, these are every 2 to 3 months for the first 2 to 3 years - once normal levels have been established. Will there be any future precautions to be aware of?
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