Thyroid disease in children

Although thyroid disease occurs less frequently in children than in adults, the signs and symptoms can be similar. However, there are a few important differences that need to be brought to light.

The thyroid gland is located at the front of the neck, just below the Adam's apple. It is responsible for the rate of all metabolic and chemical processes in our body, and affects every cell, tissue, and organ. The thyroid gland is therefore essential for life, growth and development.

Thyroid gland disorders consequently have a profound effect upon the human body.

When the thyroid gland produces too much thyroid hormone (overactive), the condition is called hyperthyroidism. When the thyroid gland produces too little thyroid hormone (underactive), the condition is called hypothyroidism.

Children with thyroid conditions are generally managed by a paediatric endocrinologist or a paediatrician in consultation with a paediatric endocrinologist.

Congenital hypothyroidism

Congenital hypothyroidism is a disorder that affects infants at birth, and occurs in about 1 in 4000 live-born babies. It is characterised by the loss of thyroid function, due to the thyroid gland failing to develop normally. In some cases, the gland is totally absent. About 10 per cent of cases are caused by an enzyme defect leading to deficient hormone production, iodine deficiency and a brain pituitary gland abnormality. If the diagnosis is delayed, and immediate treatment is not given, congenital hypothyroidism can lead to growth and developmental defects, and severe mental retardation (cretinism).

Fortunately, routine testing for thyroid function in newborns has been mandatory since 1976. Within the first week of life, a heelprick blood sample is taken to assess an infant's thyroid hormone level. If any abnormality is found, a repeat blood sample is taken. If this confirms congenital hypothyroidism, the infant is immediately given thyroid hormone replacement therapy (T4 — thyroxine). Normal growth and development should then continue, with no adverse effects on the child's mental capacity.

Before newborn thyroid screening began, this condition was easily missed. Even within a few days, subtle symptoms would emerge, such as poor feeding, constipation, low body temperature, cool skin, slow pulse, prolonged jaundice, increased sleepiness, and decreased crying. After a few weeks, other physical signs would become more noticeable, such as poor growth and development, dry skin and hair, poor muscle tone, slow tendon reflexes, hoarse crying, enlarged tongue, umbilical hernia, and puffiness or swelling. By this time, there would already have been some devastating consequences. Treatment with thyroid hormone replacement would have resolved most of the physical symptoms, but the child would more than likely have had permanent brain damage.

Hyperthyroidism in newborns

Hyperthyroidism, an overactive thyroid gland, is seen only occasionally in newborns. This condition is referred to as neonatal hyperthyroidism.

If the mother has Graves' disease, the thyroid-stimulating antibodies in her blood can cross the placenta and stimulate the unborn child's thyroid gland, thus producing too much thyroid hormone. These stimulating antibodies can be measured and are helpful for predicting the risk of an affected infant. Some newborns may hardly be affected if the levels of antibodies are low. No treatment may be necessary as the mother's antibodies will soon clear from the baby's bloodstream, usually within 2 to 3 months.

However, in rare circumstances, the levels of stimulating antibodies are enough to cause severe thyrotoxicosis. Immediate treatment with antithyroid medication will be given to correct the hormone imbalance.

Newborns with advanced hyperthyroidism may display similar symptoms to those in adults, such as an extremely fast pulse, irritability, flushed moist skin, and a ravenous appetite with failure to thrive (i.e. the infant's body tends to be long and thin).

Fortunately, treatment with antithyroid drugs is safe and effective, and will only be needed for a short period of time, until the stimulating antibodies pass from the baby's bloodstream. If the mother is on a high dose of antithyroid medication, the diagnosis can be delayed by about a week until the infant clears the antithyroid medication. Liaison with a paediatric endocrinologist is recommended prior to birth.

Hashimoto's thyroiditis

The most common cause of hypothyroidism in children and adolescents is Hashimoto's thyroiditis, an autoimmune disease. Here, the body's own immune system attacks the thyroid gland and interferes with the production of thyroid hormones. The onset of this condition can occur at any age, and the diagnosis may be easily overlooked for years, as the symptoms of hypothyroidism develop very slowly. As the thyroid gland becomes increasingly underactive, physical and mental changes will become more obvious.

Often the first sign is that the child's growth rate decreases unexpectedly and skeletal development is delayed. The child may also have an obvious swelling of the neck (goitre), as the thyroid gland becomes inflamed. Other symptoms may emerge, such as unusual tiredness or lethargy, dry itchy skin, increased sensitivity to cold, weight gain or generalised swelling, poor concentration, decreased energy, and constipation.

If hypothyroidism is suspected, a simple blood test is taken, measuring the levels of thyroid hormone and thyroid stimulating hormone (TSH), in the blood. The presence of thyroid antibodies (anti-thyroperoxidase and anti-thyroglobulin) is also helpful in confirming the diagnosis.

Treatment
The treatment for Hashimoto's thyroiditis in children and adolescents is the same as in adults. Thyroid hormone replacement is taken daily for life. The dosage of thyroid hormone needs to be age-appropriate, as the body's demands for thyroid hormone vary with age. Regular thyroid function tests will need to be assessed by a doctor to ensure that normal hormone levels are maintained.

Side effects
For those children and adolescents being treated for hypothyroidism, the results are mainly positive. The majority of their symptoms will disappear, and the body's time for 'catch-up' growth will begin. An increase in bone development will also occur. However, in children who have had long-standing hypothyroidism, ultimate height potential may be partly lost. As the child regains normal thyroid function, behavioural problems may arise as their physical and mental processes speed up. An increase in energy and alertness may lead to a decreased attention span and a loss of concentration, especially in school. Teachers should be made aware of the child's condition, as well as treatment and possible changes in behaviour. Over time, any problems with behaviour, or at school, will resolve.

Graves' disease

The most common cause of hyperthyroidism in children and adolescents is an autoimmune condition called Graves' disease. In Graves' disease the body produces antibodies that stimulate the thyroid gland uncontrollably, to make too much thyroid hormone. Children can have similar symptoms to adults, although they are less likely to complain about them. Initially the most prominent sign of this condition may be that the child displays increased energy. They may appear hyperactive and restless, be noisier in class, and easily distracted. This may lead to poor academic performance, and parent frustration. A child's hyperthyroidism may not be diagnosed until more pronounced signs and symptoms appear. These include an enlarged thyroid gland. Other symptoms include a fast pulse, nervousness, heat intolerance, weight loss, accelerated growth rate, shaky hands, muscle weakness, diarrhoea, and sleep and behavioural disturbances. Thyroid eye disease is very rare in young children.

Once a thyroid disorder is suspected, a simple blood test is performed to measure the levels of thyroid hormones and thyroid stimulating hormone (TSH) in the blood. The presence of thyroid-stimulating antibodies may also be helpful in confirming the diagnosis. If test results come back positive, then appropriate treatment is commenced immediately.

Treatment
Treatment of hyperthyroidism in children initially involves the use of antithyroid drugs, such as propylthiouracil (PTU) or carbimazole, and if well tolerated, these may be continued for months or even years. For some children, these drugs alone stabilise their condition, and no further treatment is needed. For some, a period of 'block and replace therapy' (antithyroid drugs as well as thyroxine) is useful. For others, surgery or even radioactive iodine may be necessary, depending on the severity of their thyroid disorder, or their response to antithyroid drugs. Throughout a child's treatment, thyroid hormone levels will need to be monitored regularly, along with their clinical symptoms.

Side effects
In children and adolescents with Graves' disease, the main difficulties usually occur before treatment is initiated. Once their condition is under control, their physical and mental capabilities return to normal. Antithyroid drugs can, however, occasionally stop the production of white blood cells or platelets. Sore throats, mouth ulcers, excessive bruising or skin rashes can indicate this. Patients should stop taking their medication and see their doctor immediately or attend the casualty department at their local hospital to test whether their blood cells or platelets are normal. Of course, these symptoms are common and it is most likely that they are not due to the antithyroid drugs. However, the only safe action is to stop the medication until after the result of the blood test.

Parent involvement

Parent involvement is vital for children and adolescents receiving treatment for their thyroid disorder. They will need to supervise the taking of medication on a daily basis, and carefully monitor their child's progress. They will also need to be aware of the signs and symptoms of under- or over-medicating, so they can work with their doctor to obtain the right level of medication.

As children grow, it is important for parents to keep close track of their child's thyroid hormone levels, as periodic changes in dosage will occur with changes in age. Doctors often recommend that a child have blood tests at least every 3 to 6 months. Some children may have a tendency to neglect their medication regimen, and this may lead to symptoms reappearing.

Thyroid disorders can run in families, so it is important to let your doctor know of your family background. If close family members have either hypothyroidism or hyperthyroidism, then it would be wise to keep a close eye on children in the family. Girls tend to be especially prone to developing thyroid problems, due to hormonal changes throughout their life.

In summary, the signs and symptoms of thyroid disease are similar in children, adolescents, and adults. However, there are a few key differences that relate to growth, development and behaviour. If children are treated early and appropriately, with regular monitoring, they will grow and develop normally, and enjoy life as a child.

Robyn Koumourou


 
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