What is hyperthyroidism, and how is it diagnosed?
Written by:Top Doctors recently chatted with highly qualified and experienced consultant endocrinologist, Dr Teng-Teng Chung, to talk all about hyperthyroidism, including the causes, symptoms, and diagnosis.
What is hyperthyroidism?
Hyperthyroidism means an overactive thyroid gland. The thyroid gland sits at the front of your neck and is a butterfly shaped gland. It produces the thyroid hormone. The thyroid hormone is required to keep your metabolism normal and, therefore, cells require it to function normally. In hyperthyroidism, you produce more thyroid hormone than the body requires.
Symptoms usually include:
- unintentional weight loss
- palpitations/fast heart beat
- sweating and heat intolerance
- trembling hands
- diarrhoea
- irritability/anxiety/disturbed sleep
- irregular periods
- tiredness and feeling weak
- a change in the appearance of your eyes
- an enlarged thyroid gland
What are the most common causes?
The most common cause is when your immune system does not recognise your thyroid cells, and, as a result, destroys them. Another cause is elevated levels of pregnancy hormone (βHCG), seen in severe morning sickness. This can cause a transient hyperthyroidism, which often settles after the first trimester.
How is it diagnosed?
It is easily diagnosed through a simple but accurate blood test to check thyroid function. Normally, in an overactive thyroid, your thyroid stimulating hormone (TSH) level is decreased (below the reference range) and thyroxine (T4) is high (above the reference range). Antibody levels (TSH receptor antibodies) will also be checked.
What is the outlook in terms of treatment?
Anti-thyroid medication in the form of tablets such as carbimazole or propylthiouracil can be highly effective. Treatment needs to be taken every day for a minimum of between 12 to 18 months. Other treatment options include surgery to remove the thyroid gland, or, in some cases, patients are more suited to radioactive iodine, a radioactive tablet taken to suppress the thyroid gland.
How does hyperthyroidism affect pregnancy?
During the first 12 weeks of pregnancy, the baby is entirely dependent on the mother for the thyroid hormone. After 12 weeks, the baby begins to produce its own thyroid hormone, but still requires iodine from the mother’s diet.
Will my thyroid problem affect my baby?
It is important for your baby’s health that your overactive thyroid is treated. If your thyroid is untreated, the baby can develop a very fast heart rate (foetal tachycardia), it can be born small or premature and there is a higher risk of stillbirth and congenital malformations.
Will my thyroid problem affect me in pregnancy?
No, if treated. For patients who become pregnant with untreated overactive thyroid, their chances of developing a life-threatening condition called thyroid storm are increased and the risk of pre-eclampsia (a very serious condition) in your pregnancy is also increased.
Can Graves’ disease adversely affect pregnancy?
If you have Graves’ disease or history of this, there is a chance that TSH receptor antibodies (TRAB) produced could cross the placenta and start to attack the baby’s thyroid causing it to overact. TRAB should be checked when you become pregnant, and then usually again in your third trimester after six to seven months, so that your baby can be monitored and treated if necessary.
Will anti-thyroid drugs affect my baby?
Both carbimazole and propylthiouracil do cross the placenta and hence should be used in the lowest dose possible. Carbimazole has been associated with an increased risk of birth defects if used within your first ten weeks of pregnancy. The risk of defects such as bald patch (aplasia cutis), abdominal wall defects, and cardiac defects is between two to four per cent. Based on medical evidence, it is advised that propylthiouracil should be used before conception and during the entirety of your pregnancy.
Well-controlled hyperthyroidism will improve chances of fertility. An untreated overactive thyroid will impair your fertility and make it difficult for you to become pregnant and could also complicate your pregnancy. It is vitally important that patients inform their endocrinology team as soon as they become pregnant in order to perform TFT to optimise medication dose.
Depending on the TFT result, you will be reviewed between every four to eight weeks during your pregnancy. If blood tests are stable, this would normally be checked every six to eight weeks. Upon delivery, if there has been any concern with regards to the baby’s thyroid, a paediatrician will promptly review the baby after birth.
Graves’ disease may become worse within the first three months after delivery, so often, your anti-thyroid drug is increased. If you wish to breastfeed, it is safe to do so whilst taking carbimazole up to 20mg daily or propylthiouracil up to 450mg daily.
If you would like to book an appointment with Dr Teng-Teng Chung, simply head on over to her Top Doctors profile to do exactly that today.
