Thyroid During Pregnancy : Reasons, Signs & Treatment

Thyroid Disease in Pregnancy

Medically Reviewed By
Dr. Sabiha Anjum (Gynecologist/Obstetrician)
View more Gynecologist/Obstetrician Our Panel of Experts

As soon as your pregnancy is confirmed by your gynaecologist, you will be asked to take a thyroid test. You may also have to take one if you are planning to conceive. Although thyroid during pregnancy is a common condition, there is a possibility of confusing it with other regular pregnancy symptoms due to its similarities. Symptoms like weight gain, feeling tired, getting moody or forgetful and even swelling up are common to pregnancy and thyroid condition. Thus it is all the more important to identify any symptoms of thyroid in advance to treat or manage the situation in ways that don’t affect the pregnancy. Read on to know more.

Video : Why You Should Check for Thyroid During Pregnancy?

What Is Thyroid Disorder?

The H-shaped thyroid gland is placed at the front of our neck, right below the voice box. It is about two inches long and is almost weightless (less than an ounce). It forms an integral part of the endocrine system, which does the vital job of producing hormones for your body. The thyroid gland produces two major hormones, T3 (triiodothyronine) and T4 (thyroxine). The hormones created by your thyroid control your body’s metabolism and many other vital bodily functions like weight, brain development, breathing functions, body temperature and cholesterol levels. It is important to monitor thyroid levels in pregnancy since it can have a telling impact on the baby inside the womb (including the neuron intellectual abilities).

Thyroid during pregnancy is common when a woman is in her prime childbearing age, but if it is not diagnosed in time, its impact can extend well beyond pregnancy. The condition is classified as – hyperthyroidism and hypothyroidism. While hyperthyroidism is caused due to high levels of hormones in the blood, hypothyroidism is caused due to decreased levels of thyroid hormones in the blood.

How Does Pregnancy Affect Thyroid Function

During pregnancy, two hormones, oestrogen and human chorionic gonadotropin (hCG) are responsible for enhancing your thyroid levels. These thyroid hormones play a vital role in the development of the baby’s brain and nervous system, and your health when you are pregnant.

The placenta makes hCG, which is similar to TSH (thyroid-stimulating hormone) and stimulates the thyroid to create more hormones. Increase in oestrogen levels produces thyroid-binding globulin, a protein that helps thyroid hormone to travel in the blood. In the first trimester, your baby is dependent on you for its thyroid hormone needs, which come through the placenta. This will go on until the 12th week, after which the baby’s thyroid will begin functioning on its own.

How Does Pregnancy Affect Thyroid Function

It is necessary to conduct a thyroid function test to detect any pregnancy problem due to thyroid. The thyroid does increase in size during pregnancy, but that is not enough to conclude the test. Thyroid related issues may be difficult to diagnose during pregnancy because many pregnancy signs seem similar to the symptoms of thyroid disorders, such as an increase in the thyroid hormone level, fatigue and increase in the size of the thyroid.

Let’s take a look at both the conditions a little in detail.

Hyperthyroidism in Pregnancy

When an overactive organ produces thyroid hormone in large quantities, the condition is known as hyperthyroidism. Read on to know the causes, symptoms, diagnosis, treatment, etc. of the condition in pregnancy.

1. Causes of Hyperthyroidism in Pregnancy

Hyperthyroidism is usually caused by Grave’s Disease, which is an autoimmune disorder in which the immune system attacks its cells and organs instead of protecting it. Toxic Adenomas is also another cause of hyperthyroidism, wherein nodules that grow in the thyroid gland begin secreting hormones. This disturbs the body’s chemical balance.

2. Who Is at Risk?

Women who have been diagnosed with hyperthyroidism before their pregnancy and those with a family history of hyperthyroidism are most likely to experience it during their pregnancy.

3. Symptoms

Fatigue, Nausea, vomiting, fast heart rate, change in appetite and growth of thyroid levels and thyroid size are the typical symptoms of hyperthyroidism. One can also notice changes in appetite and lower tolerance to heat.


4. Diagnosis

By carrying out three major tests to diagnose hyperthyroidism, it is possible to diagnose the condition in pregnant women:

  • TSH Test – This test is capable of detecting meagre amounts of TSH (thyroid-stimulating hormone) in the blood and is known to be ultra-sensitive. TSH test is one of the most accurate tests for measuring thyroid activity.
  • T3 & T4 Test – If the TSH test shows that the levels are low, it is mandatory to carry out T3 (triiodothyronine) & T4 (thyroxine) tests. If free T4 (the part of thyroid hormone unattached to thyroid-binding protein) levels are found to be elevated, the diagnosis is confirmed.
  • TSI Test – TSI (thyroid-stimulating immunoglobulin) test is conducted if a pregnant woman has had radioactive treatment or surgery or has been diagnosed with Graves’ disease. This test confirms the presence of TSI antibodies in a pregnant woman’s body.

5. Treatment

Treatment is not required for mild hyperthyroidism where TSH levels are low, but free T4 is normal. In case of a severe thyroid disorder, the doctor prescribes propylthiouracil (PTU), in low doses during the first trimester. Anti-thyroid medication, methimazole is prescribed after the first trimester if necessary. In rare cases where the patient does not respond to medication, surgery may be suggested to remove a portion of the thyroid. Radioactive iodine treatment is not recommended for pregnant women since it can damage the baby’s thyroid gland.

Can Hyperthyroidism Affect the Mother and the Baby?

Yes, hyperthyroidism can affect the mother and the baby. There are high chances of the condition leading to preeclampsia, premature birth, miscarriage and sudden worsening of hyperthyroid symptoms in the mother. Also, a newborn can suffer from rapid heart rate leading to heart failure, poor weight gain, low birth weight, irritability and enlarged thyroid causing breathlessness.

Hypothyroidism in Pregnancy

The deficiency of thyroxine, the thyroid hormone, which occurs due to an underactive thyroid gland, is known as hypothyroidism.

1. Causes of Hypothyroidism in Pregnancy

A low level of thyroid hormones in the blood causes this condition, where the thyroid gland functions inadequately. Removal of the thyroid, endemic goitre, iodine deficiency, radiation therapy and diseases related to the pituitary gland are its other causes. Hypothyroidism in pregnancy is also caused due to Hashimoto’s disease, which is a form of inflammation of the thyroid.

2. Who Is at Risk?

Women who have a family history of hypothyroidism or have been diagnosed with this condition in the past are at risk of developing this condition during pregnancy.

3. Symptoms

Common symptoms of hypothyroidism include a swollen face, fatigue, intolerance to cold, weight gain, lower concentration levels, skin tightening or stretching and abdominal discomfort. Decreased levels of T4 and high TSH levels are indicators of hypothyroidism, too.

Symptoms of Hypothyroidism

4. Diagnosis

To confirm the condition, your doctor will check if you show any of the above-mentioned symptoms and ask you to get FT3 (free T3) and FT4 (free T4) tests done in pregnancy as they have high chances of being accurate.

5. Treatment

During pregnancy, hypothyroidism is treated by starting on thyroxine, a synthetic thyroid hormone. Thyroxine is beneficial for the mother and the child and is safe for them, too. Women who have developed this condition before pregnancy should increase their dosage after speaking to their doctor, to maintain thyroid function.

Can Hypothyroidism Affect the Mother and the Baby?

Hypothyroidism can cause preeclampsia, anaemia, stillbirth, miscarriage, and in rare cases, congestive heart failure. Thyroid hormones are essential for the growth and development of the baby’s brain and nervous system. Hypothyroidism can affect their development, especially if it occurs in the first trimester.

Is it Safe to Consume Thyroid Medications During Pregnancy?

Yes, it is safe to consume thyroid medications during pregnancy. In fact, it is unsafe to keep hypothyroid or hyperthyroid conditions untreated while one is pregnant. Medication should be taken and should be monitored closely. Levothyroxine is a synthetic form of thyroid hormone that is baby-safe and is commonly used to treat this condition.

Diet, Nutrition and Dietary Supplements for Hypothyroidism

The body demands high amounts of nutrients during pregnancy as it needs to balance the mother and baby’s health. During this period, doctors recommend the mother-to-be to follow a balanced diet and derive the necessary nutrients from prenatal vitamins and iodine-based mineral supplements.

Pregnant women diagnosed with hypothyroidism should ensure that they get the recommended dose of iodine through daily food and replacing iodised salt with normal salt is one way of doing it. Eating greens like spinach, fenugreek and lettuce leaves provide magnesium, which is necessary for the functioning of the thyroid. Blueberries and strawberries are great for the immune system and contain antioxidants, so make sure they are a part of your diet. Include eggs, walnuts, mushrooms and fish like salmon in your diet to get Omega 3 fatty acids and selenium to regulate hormones the natural way. Vitamin B6 is especially beneficial in pregnancy.

Woman taking pills

How to Avoid Thyroid Complications During Pregnancy

Your thyroid controls every cell in your body, and without its presence, the body slows down resulting in fatigue, weight gain, hair loss and much more. Here is how you can prevent thyroid and pregnancy complications from affecting your body and the baby:

  • Stay away from diets that recommend starvation for long periods. Fasting results in a huge reduction of T3 levels which enhances metabolism.
  • The thyroid gland is susceptible to x-rays. Make sure you ask for a thyroid shield whenever you undergo radiation during pregnancy.
  • If you are pregnant and have been smoking, it is time to stop. Those with a predisposition for thyroid are at higher risk. A study suggests that smoking increases the risk of hypothyroidism, especially for patients with Hashimoto’s thyroiditis.
  • To reduce the effect of thyroid on pregnancy, women with borderline hypothyroid should begin with a low dose thyroid hormone at the beginning of pregnancy.

It is necessary to keep reviewing the symptoms of hyper and hypothyroidism during pregnancy, for which repeated testing of TSH levels is needed. Speak to your doctor if you observe any symptoms so that precautionary measures can be taken. By checking your thyroid levels, you can look forward to a safe and hassle-free pregnancy.

Also Read: 22 Infections That Can Affect Your Pregnancy

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