Who should be tested for a thyroid disorder?

In this article below, distinguished consultant endocrinologist, Dr Teng-Teng Chung, discusses thyroid disorders during pregnancy, before also detailing what hypothyroidism is.

How important is it to get treatment for a thyroid disorder during pregnancy?

An uncontrolled or undiagnosed thyroid disorder will impair women’s fertility and potentially cause problems during pregnancy.

Who should be tested?

There are certain patients who should definitely be tested for a thyroid disorder. For example, someone who should be tested is someone who is planning for fertility and who has a history of thyroid disease such as:

• hypothyroidism
• subclinical hypothyroidism
• previous history of radioactive iodine
• previous history of thyroid surgery
• hyperthyroidism or Graves’ disease
• thyroiditis or positive TPO antibodies

What is hypothyroidism?

The most common type of thyroid disorder in child-bearing women is hypothyroidism. Hypothyroidism means an underactive thyroid gland. The thyroid gland sits at the front of your neck and is a butterfly shaped gland.

It produces thyroid hormone. Thyroid hormone (thyroxine) is required to keep your metabolism normal, and therefore cells require it to function normally. In hypothyroidism, you do not produce enough thyroid hormone, and as a result, your metabolism and cells slow down. It is a very common condition that affects one in 50 women.

What are the symptoms of hypothyroidism?

There are a host of related symptoms. The main ones include the following:

• weight gain
• constipation
• dry skin
• dry and thinning hair
• muscle pains or pins and needles
• heavy periods/ fertility problems
• poor concentration and poor memory
• low mood
• fatigue and tiredness

What are the main causes?

The most common causes of hypothyroidism are:

• autoimmune (the most common): the immune system does not recognise your thyroid cells and destroys them
• radioactive iodine (treatment used for overactive thyroid
• thyroid removal via surgery
• head and neck radiotherapy for cancer
• problems to your pituitary gland (the hormone centre in the brain)

How is it diagnosed?

It is easily diagnosed through a simple blood test called a thyroid function test (TFT). Normally, when your thyroid is underactive, your thyroid stimulating hormone (TSH) level is increased (above the reference range) and thyroxine (T4) is low (below the reference range).

How is hypothyroidism treated?

Treatment involves the replacement of thyroxine in tablet form which has to be taken every day and usually for a long period of time. Thyroxine tablets should usually be taken first thing in the morning approximately 30-60 minutes before food, hot beverages, such as coffee and multivitamin tablets (including iron, calcium and anti-reflux tablets).

How does hypothyroidism affect pregnancy?

During the first 12 weeks of pregnancy, the baby is entirely dependent on the mother for 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 the health of your baby that your underactive thyroid is treated. The thyroid hormone plays a key role in the development of your baby’s nervous system (brain).

Will my baby have thyroid problems?

Most babies are born with a fully functioning thyroid. Hypothyroidism is routinely checked for in newborn babies as it is checked during the “heel prick” test. Congenital hypothyroidism is rare in babies (about one in 2,000 to 3,000 in UK) and in most cases the cause is unknown and there is no way to prevent it.

Is thyroxine safe to take in pregnancy?

Thyroxine is a naturally produced hormone and is therefore safe to take in pregnancy. When planning your pregnancy, it is ideal that your TFT is checked to ensure you are on the correct dose of thyroxine treatment. If your thyroid is appropriately treated and your TFT are within the normal level, there is no reason why you should not be able to fall pregnant.

Once your pregnancy is confirmed, you will be advised to increase your thyroxine dose by 25 mcg daily. This is normal practice to ensure you and your baby have enough thyroid hormone during your pregnancy. One exception is women with thyroid cancer and are already on doses of thyroxine that keep their TSH level suppressed. These women probably do not need to increase their dosage but will need to discuss further with their specialist.

What should I do during my first trimester of pregnancy?

There are many things one should do during their first trimester of pregnancy. These include: 

• you should have a recent TFT to be receive the best advice in relation to your thyroxine dose
• your TFT should be checked between every four to six weeks during the first trimester
• if you suffer with morning sickness, your thyroxine can be taken at night time before bed

During your second and third trimester of pregnancy, your TFT should be checked at least once every trimester. If there is a change in your thyroxine dose, then your TFT should be checked again within four to six weeks. Once you deliver, you should go back on to pre-pregnancy thyroxine dose and have TFTs checked after six to eight weeks after delivery.

To consult with Dr Teng-Teng Chung, visit her Top Doctors profile today.