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.
Here is Dr Tim's summary of some of the latest research news that is taking place with regard to children and thyroid disorders.
The National Thyrotoxicosis Study: This is a study that is looking at how best to administer anti-thyroid drug (almost always carbimazole in the UK) to children and adolescents. Recruitment was slow at first but following a grant from the BTF in 2008 this accelerated and over 80 patients have been recruited from around 15 centres in England, Scotland and Wales. The study involves quite a lengthy period of follow-up and we have been trying to obtain funding to support the study for the next few years.
Radioiodine administration to young people with thyrotoxicosis: The paediatric endocrinology and the medical physics department in Newcastle has been looking at patterns of radioiodine administration to young people with thyrotoxicosis in Great Britain. Families seem to be choosing this treatment more often and it is being administered at a progressively younger age. We are looking to publish this data in the near future.
Congenital hypothyroidism in the UK and how paediatricians manage the condition: The British Paediatric Surveillance unit study, which is looking at the incidence of congenital hypothyroidism in the UK and how paediatricians manage the condition initially, has been underway for a year and we are now at a point where we can start analysing some of the results. The study is supported by the Royal College of Paediatrics and Child Health and received backing from the BTF.
Read about the Newborn Bloodspot Screening Wales Project. This is the latest issue of the bulletin of the newborn screening programme in Wales. The purpose is to create a nationwide screening programme that is uniform to the country.
Congenital hypothyroidism (CHT) will be added to the ‘Orange Card’ for one year from June 2011.
A newborn screening programme for congenital hypothyroidism was first introduced in the early 1980’s so many paediatricians might assume that there is not much more to learn. However several important questions remain unanswered and this collaborative BPSU study has been designed to make a major contribution to answering them and, in the process, provide valuable insights into ways to improve patient outcome. This is an important initiative and strongly supported by the BSPED and ESPE, as well as parent organisations, because of its benefits for patient care.
A key aim of the study is to determine how many babies and children are diagnosed each year with CHT, and whether this follows a positive newborn screening result or clinical presentation. Of particular interest are the children who turn out to have transient fluctuations in hormone levels.
In the UK, around 470 children are referred annually for further investigations after a positive screening result for CHT. However, the programme currently has no reliable information about individual diagnostic outcomes and how these relate to screen positive results or screening laboratory cut-off levels (which vary throughout the UK). This study will provide valuable information about the performance of the current UK screening programme for children with suspected CHT, patterns of clinical service provision, management and care, as well as outcomes in the first two years after diagnosis.
A novel aspect of this BPSU study is that we will be using an online questionnaire system, designed to be easier to complete and submit than paper questionnaires, especially for clinicians who regularly see children with suspected CHT. Any paediatrician who reports a case will receive a link by email to the online questionnaire shortly after notification, making the reporting system much more efficient. The National Information Governance Board and Research Ethics Committee have approved the high-level security in this new data collection system and the BPSU and study investigators will also want to hear your views on how well this new system is working.
‘Congenital’ is a word that is often used by doctors and it basically means ‘present at birth’.
There are two major types of congenital thyroid disease – one that involves a baby being hypothyroid (or ‘under-active’) and one that involves a baby being hyperthyroid (or ‘overactive’).
The hypothyroid form of congenital thyroid disease – congenital hypothyroidism (CHT for short) - is much more common than the hyperthyroid form. In the UK, as in many other countries in Europe, every newborn baby is screened for CHT in the first days of life. This is because it can be treated so effectively with thyroid hormone replacement.
CHT is usually the result of a poorly developed thyroid gland or one that has developed in the neck but has an inherent thyroid ‘manufacturing’ problem.
Hyperthyroidism is where there is too much thyroid hormone in the body. Most family doctors will have seen this condition in their surgery in older teenagers and adults but it can occasionally occur in babies as well. When a baby is hyperthyroid it is usually because antibodies cross the placenta in pregnancy from a mother who has a history of thyroid gland problems. The antibodies act like a switch and tell the babies thyroid gland to work too hard. Whilst CHT can be detected through the newborn screening test, hyperthyroidism is usually detected when the doctor or nurse examines the newborn baby and notices that things aren’t quite right. Sometimes the midwife or doctor will pick up on the fact that mum has a history of thyroid problems and the baby will be monitored more closely during pregnancy as a result. The treatment of thyroid gland overactivity includes a type of medicine that ‘slows’ the thyroid gland down to normal.
Babies with either of these conditions (CHT and hyperthyroidism) are at risk of abnormal growth and developmental problems if it is not diagnosed and treated appropriately. Thankfully this is rarely the case now.
When a baby is diagnosed with congenital thyroid disease, the parents will usually need to come to hospital regularly in the first weeks of life to make sure that treatment is going according to plan. Children with CHT will typically require monitoring in hospital throughout childhood and into adult life but hyperthyroidism in babies is usually a temporary problem and so babies can be discharged once they are off all treatment.
Many parts of the human body can stop working properly in people of all ages and the thyroid gland is no different. In the next few paragraphs I will tell you about the two main reasons why the thyroid gland can fail to produce enough thyroid hormone. This is usually called hypothyroidism or thyroid gland under-activity. Sometimes when the thyroid gland stops working properly it makes too much thyroid hormone but this is a different problem that I will tell you about in another edition of this newsletter.
There are two main kinds of under-active thyroid gland or hypothyroidism:
The first cause of hypothyroidism affects children before they are born. This is often called ‘congenital hypothyroidism’, which means you were born with it. In congenital hypothyroidism the thyroid gland usually does not develop properly so that it is very small or completely absent. This is the case in four out of five babies with congenital hypothyroidism. One way of thinking about this is that the thyroid gland factory has not been built or has only partially been built. In one in five children with congenital hypothyroidism, however, the gland has formed but doesn’t have the manufacturing equipment to make thyroid hormone. In other words the thyroid gland factory has been built but the production line is broken.
It is important to detect congenital hypothyroidism as soon as possible after birth and all babies in the UK have a heel-prick blood test in the first days of life to pick this problem up. If babies are found to have an under-active gland by the heel-prick test then they are treated as soon as possible because thyroid hormone is very important in the first two years of life so the baby will develop and grow properly.
Autoimmune thyroid disease
The second cause of hypothyroidism affects children and teenagers rather than babies and is called ‘autoimmune thyroid disease’. In this condition the body mistakenly thinks that the thyroid gland is ‘an enemy’ and so it attacks and potentially destroys the gland. We sometimes call this a ‘friendly fire’ problem in our clinic because the body’s defences are attacking the thyroid gland by mistake. Sometimes the thyroid gland can get bigger when it is under attack and sometimes it gets smaller and is destroyed completely. Sometimes the body’s defences attack the gland over a long period of time and sometimes the body’s defences settle down and leave the thyroid gland alone.
The good news is that if the thyroid gland fails to produce enough thyroid hormone then it is usually quite straightforward to treat it with replacement thyroid hormone. Treatment is important because if the thyroid gland does not produce enough thyroid hormone this can make someone tired, sleepy and not at their best. It can also prevent young people from growing properly.
To summarise ...
The treatment of young people with either congenital hypothyroidism or an under-active thyroid gland because of autoimmune thyroid disease is really the same. In both conditions, daily thyroid hormone medicine (usually tablets but sometimes liquid) is a successful way of putting back what the thyroid gland should be making. It does mean regular blood tests although this is usually only necessary every three to six months by the time a child is going to school.
People with thyrotoxicosis have a thyroid gland that is 'over-active' and so makes too much thyroid hormone.
Thyrotoxicosis affects people of all ages including children. Most people have it because they have developed antibodies to the thyroid gland. Usually these antibodies include some that directly switch the thyroid gland ‘on’ (a bit like flicking on the light switch at home). The antibodies that switch the gland on are a feature of Graves’ disease which is the most common cause of thyrotoxicosis in young people. Not everyone with thyrotoxicosis has Graves’ disease though. Sometimes the antibodies cause the release of too much thyroid hormone in the absence of the ‘switching on’ antibodies that are characteristic of Graves’ disease.
Girls develop thyrotoxicosis more often than boys. Less than one in 100,000 people per year under 15 years old get thyrotoxicosis so it is not common!
Thyrotoxicosis can affect most parts of the body. The symptoms can include weight loss (even when you’re eating a lot!), growth spurts so you grow faster than you should, feeling too hot even in cold weather, loose bowels, mood swings and feeling irritable, having difficulty concentrating and sitting still in school so your teachers start to get cross.
Thyrotoxicosis can also be associated with heart problems such as an abnormal heart beat, leaking heart valves, and the development of weak bones. Young people may be affected for months, or even years, before a diagnosis is made. The good news however is that the majority of people with thyrotoxicosis soon get back to normal on treatment.
Young people are usually treated with anti-thyroid drugs (ATD). The ATD (usually a drug called carbimazole) can be used in one of two ways. The first way is as part of a block and replace (BR) regime: the anti-thyroid block the thyroid gland from producing any thyroxine. Then levothyroxine is added to replace the body’s natural thyroxine. This lets the doctors control how much thyroxine you have in your body so your thyroid can’t give you too much anymore.
The second way is to use a dose titration (DT) regimen, where the dose of the anti-thyroid drug is adjusted so that the amount of hormone made is just right.
Unfortunately, about 70% of the time the thyrotoxicosis returns when the ATDs are stopped. We are doing research now to find out the advantages and disadvantages of the BR and DT approaches. We want to find the best way of keeping thyroid hormone levels normal during treatment (not moving up and down so much) and the treatment that is lost likely to stop the overactivity coming back when the medicines are stopped.
If the thyrotoxicosis returns some people decide to start anti-thyroid drugs again. If they don’t want to the choice is either surgery to remove the thyroid gland or radioactive iodine (RAI).
Thyroid surgery is safe when conducted by skilled and experienced surgeons. There is a scar but it usually fades quite dramatically with time.
RAI involves taking a pill or drink of radioactive iodine that goes straight to the over-active thyroid gland where it is concentrated and destroys the thyroid gland. The RAI doesn’t go anywhere else in the body but the thyroid. In North America doctors are big fans of RAI but in Europe there are still many people who think that surgery is best. That says it all - both have advantages and disadvantages and it is important to speak to experts who can talk it all through in detail with you. It will still be a matter of personal choice though! Recent work has suggested that treating young people with RAI is very safe.
Both of these treatments usually involve taking thyroxine replacement in the long term, perhaps for life, because the abnormal gland has gone away.
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