Dr Tim Cheetham, a consultant paediatric endocrinologist (a hormone specialist) at the Royal Victoria Infirmary, Newcastle Upon Tyne, continues his series of articles to help children and young people, and their parents and carers, to understand thyroid disease.
Thyroid disorders in childhood
The following are the three principle thyroid problems affecting young people:
Congenital hypothyroidism (CHT)
Babies with CHT cannot make thyroid hormone normally. This is because the thyroid gland has either
• not developed properly (thyroid dysgenesis); or
• because it is present in the usual place (in the neck) but is unable to make thyroid hormone properly because of a ‘production-line’ or ‘manufacturing’ problem ( thyroid dyshormonogenesis).
Around one in every 3,000 babies born in the UK has CHT and girls are affected more frequently than boys. About 4 in every 5 babies with CHT have thyroid dysgenesis and 1 in 5 babies have dyshormonogenesis. It is important to detect CHT as soon as possible after birth and all babies born in the UK have a heel-prick blood test in the first days of life (around day 5) to pick this problem up.
If babies are diagnosed with an under-active gland as a result of the heel-prick test they will be treated with thyroxine (T4) as soon as possible because thyroid hormone has a key role in normal growth and brain development. Thyroid hormone is particularly important for brain growth in the first two years of life.
Babies diagnosed with CHT will usually need to come to hospital regularly during the first weeks of life to make sure that treatment is providing adequate thyroid hormone replacement. By the time the child is school age visits to hospital will take place around every 6 months. A minority of babies will have a ‘transient’ (temporary) thyroid problem and so if there is any doubt about whether the problem is permanent or not then thyroxine is typically stopped briefly at around 3 years of age. If the thyroid tests become abnormal then treatment will be needed for life.
Parents and carers should be reassured that so long as their children receive regular care as recommended by their medical team the outlook for babies with permanent CHT and transient hypothyroidism is excellent.
Autoimmune thyroid disease causing hypothyroidism
Another cause of hypothyroidism that affects children (not babies) and teenagers is ‘autoimmune thyroid disease’. In this condition the body mistakenly thinks that the thyroid gland shouldn’t be there and attacks it. Doctors sometimes call this a ‘friendly fire’ problem because the body’s defences are attacking the thyroid gland by mistake. The thyroid can be affected in any of the following ways:
• the thyroid gland can get bigger when it is under attack and cause a swelling known as a ‘goitre’;
• the thyroid gets smaller and is destroyed completely;
• the body’s defences attack the gland over a long period of time and after a while the body’s defence system settles down and leaves the thyroid gland alone in the longer term.
The good news is that if the thyroid gland fails to produce enough thyroid hormone it is usually quite straightforward to treat it with replacement thyroid hormone (T4). Treatment is important because if the thyroid gland does not produce enough thyroid hormone in the longer term it can make someone tired, sleepy, grow poorly and generally not be at their best. The outlook for children and teenagers with autoimmune thyroid disease transient hypothyroidism is excellent.
Autoimmune thyroid disease causing hyperthyroidism – Graves’ disease
Most young people with hyperthyroidism (where too much thyroid hormone is produced by the thyroid gland) have a condition called Graves’ disease or ‘thyrotoxicosis’. In Graves’ disease antibodies to the thyroid ‘switch’ on the thyroid gland and lead to excessive thyroid hormone production.
Only 100 people per year under 15 years old get Graves’ disease in the UK and so it is not a common condition. Girls also develop thyrotoxicosis more often than boys.
The excess thyroid hormone affects many parts of the body. The symptoms can include weight loss (often despite a big appetite), feeling hot even in cold weather, loose bowels, mood swings and irritability. Some people have difficulty concentrating at school. Thyrotoxicosis can also be associated with heart problems such as a rapid heartbeat and leaking heart valves. Young people may be affected for months, or even years, before a diagnosis is made.
Once the diagnosis is made then initial treatment is usually with antithyroid drug (carbimazole) for around 2 to 3 years. If the thyroid gland over-activity returns when the medication is stopped then the options are to return to carbimazole or to consider ‘removing’ the gland with surgery or radio-iodine.
Both of these options (surgery and radio-iodine) will mean that the person needs thyroid hormone replacement in the longer term. With proper medical support, the outlook for people with Graves’ disease is excellent once the diagnosis has been made although most people will ultimately require thyroid hormone replacement.