Everything You Need To Know About Hyper/Hypo Thyroidism During Pregnancy

Everything You Need To Know About Hyper/Hypo Thyroidism During Pregnancy

20 Feb 2018 | 7 min Read

Sayani Basu

Author | 607 Articles

The thyroid is a tiny, butterfly-shaped gland in your neck that makes hormones that play a vital role. The thyroid hormones are responsible for regulating metabolism, the heart, nervous system, weight, body temperature, and many more processes that take place in your body. Sometimes the thyroid gland makes too much or too little of certain hormones, which triggers thyroid disorders like hyperthyroidism and hypothyroidism.

According to research, thyroid and pregnancy are an alarming duo, and approximately one in every 10 women suffers from thyroid problems in India. Some have a thyroid disorder that begins before pregnancy (a pre-existing condition), and others might develop thyroid during pregnancy or soon after giving birth.

The American Thyroid Association suggests that the normal thyroid levels in pregnancy should be maintained between 0.2-<2.5 mU/L in the first trimester of pregnancy and between 0.3-3 mU/L in the remaining trimesters. Read on to know more about thyroid during pregnancy.

What Is Hyperthyroidism?

Hyperthyroidism in pregnancy is when an overactive gland produces too much thyroid hormone and occurs in about one to four of every 1,000 pregnancies.

Hyperthyroidism in expecting mothers is usually caused by Graves’ disease, an autoimmune disorder in which the immune system makes an antibody that causes the thyroid to overproduce thyroid hormone.

Hyperthyroidism during pregnancy has also been linked to hyperemesis gravidarum (excessive nausea and vomiting), as both conditions are triggered by higher human chorionic gonadotropin (hCG) levels, a hormone produced by the placenta if you are pregnant.

Symptoms of Hyperthyroidism During Pregnancy

Hyperthyroidism in pregnancy symptoms include:

  • Fatigue
  • Severe nausea or vomiting.
  • Irregular or increased heartbeat
  • Trouble in sleeping
  • Weight loss or less weight gain than a normal pregnancy

Risks of Hyperthyroidism During Pregnancy

Untreated hyperthyroidism can lead to serious complications for both the expectant mother and the baby, including:

  • Congestive heart failure in the expecting mother
  • Miscarriage and stillbirth
  • Preeclampsia
  • Low birth weight and even premature birth
  • Thyroid storm (a sudden and severe worsening of the symptoms)
Women who have been diagnosed with hypothyroidism in the past or who have a family history of thyroid disorders are at an increased risk of it during pregnancy. | Image Source: freepik

What Is Hypothyroidism?

Hypothyroidism in pregnancy is when the thyroid is underactive and doesn’t make enough thyroid hormones. As a result, many of your body’s functions slow down.

Hypothyroidism during pregnancy is usually caused by an autoimmune disorder called Hashimoto’s disease that causes chronic inflammation of the thyroid gland.

Women who have been diagnosed with hypothyroidism in the past and those who have a family history of thyroid disorders are at an increased risk of experiencing the condition during pregnancy.

Symptoms of Hypothyroidism During Pregnancy

Some of the symptoms of hypothyroidism in pregnancy include:

  • Intense fatigue and abdominal discomfort
  • Feeling cold and memory loss
  • Extreme muscle aches and cramps
  • Excessive weight gain
  • Skin problems and hair loss
  • Constipation
  • Swelling of the face, hands, and feet
  • Lower concentration levels

Risks of Hypothyroidism During Pregnancy

If untreated, hypothyroidism during pregnancy causes:

  • Preeclampsia
  • Miscarriage
  • Premature birth and even low birth weight
  • Anaemia for the mum
  • Stillbirth

In addition to these, if left untreated, hypothyroidism can also cause congestive heart failure for the mother.

Causes of Thyroid Disease In Pregnancy

During pregnancy, thyroid diseases such as hyperthyroidism and hypothyroidism can have adverse maternal and foetal outcomes.

Here are some common causes of hyperthyroidism and hypothyroidism in pregnant women:


  1. Graves’ disease: Graves’ disease is an autoimmune disorder in which the immune system makes an antibody called thyroid-stimulating immunoglobulin (TSI) that causes the thyroid to overproduce thyroid hormone.
  1. Thyroid nodules: Thyroid nodules are lumps in your thyroid that make too much of thyroid hormones. The thyroid becomes overactive and makes too many thyroid hormones and can cause many of your body’s functions to speed up.

These nodules are generally non-cancerous and harmless. 


  1. Hashimoto’s disease: Hypothyroidism in pregnancy is usually caused by Hashimoto’s disease. It is a condition in which your immune system makes antibodies that attack your thyroid and tend to damage it. Therefore, it can’t produce thyroid hormones.
  1. Deficiency of iodine: According to medical studies, endemic deficiency of iodine is also a common cause of hypothyroidism in pregnancy worldwide.
A thyroid ultrasound helps to detect goiters of the thyroid and is painless. | Image Source: freepik

Diagnosis of Thyroid Disease In Pregnancy

Doctors don’t usually ask for thyroid tests during pregnancy unless you’re at an increased risk of having a thyroid condition or you have symptoms.

If you have symptoms of thyroid during pregnancy, it is advisable to consult a doctor.

The doctor gives you a physical exam and a blood test to check for thyroid conditions. The blood test measures the thyroid levels in pregnancy along with the thyroid-stimulating hormone (TSH) in your body.

The active hormones include Triiodothyronine (T3) and T4 (Thyroxine). T3 and T4 are regulated by the thyroid-stimulating hormone (TSH).

TSH levels that are above normal and T4 levels that are below normal might indicate that you have hypothyroidism.

Your doctor might look for antibodies in your blood to see if Graves’ disease is causing hyperthyroidism.

Treatment of Thyroid Disease in Pregnancy

Pregnant women with pre-existing thyroid diseases need to be more cautious about the medical attention they seek during pregnancy.

  • Treatment for hyperthyroidism: If you have mild hyperthyroidism during pregnancy, you might not need treatment. However, if it is linked to hyperemesis gravidarum, you will need treatment for vomiting and dehydration.

If your hyperthyroidism is more severe, your doctor can also prescribe anti-thyroid medicines.

Doctors often treat pregnant women with the antithyroid medicine propylthiouracil during the first three months of pregnancy. Another type of antithyroid medicine, methimazole is also prescribed.

  • Treatment for hypothyroidism: Doctors usually prescribe a synthetic form of T4 (levothyroxine) to replace the missing hormone.

The dose is adjusted regularly to maintain a steady blood level of thyroid hormone within the normal range.

Since the requirements for this hormone might increase during pregnancy, it is routine practice to monitor the blood level of the thyroid-stimulating hormone (TSH) during pregnancy.

Often, mums ask questions like, “Does thyroid affect pregnancy”? With treatment, thyroid in pregnancy might not cause any problems during pregnancy. On the other hand, if left untreated, the thyroid effect on pregnancy can be severe.


Why is a thyroid test done during pregnancy?

A thyroid test is done during pregnancy as an accurate assessment of thyroid function is critical for both the initiation of thyroid hormone therapy and for the adjustment of thyroid hormone dose in those already receiving thyroid hormone.

When is a thyroid test done during pregnancy?

Your doctor will most likely test your thyroid hormone levels every four to six weeks for the first half of your pregnancy, and at least once after 30 weeks.

Will the thyroid affect the baby during pregnancy?

Untreated thyroid conditions during pregnancy can affect the fetus, including premature birth, low birth weight, miscarriage, and stillbirth.

Does thyroid affect normal delivery?

If left untreated, thyroid disorders can affect both the expectant mother and the baby, irrespective of the type of delivery.

What are the early warning signs of thyroid problems?

Some of the early warning signs of thyroid problems include fatigue, weight changes (weight gain and loss), sensitivity to heat and cold, swollen face, hands, and feet along with increased and slowed heart rate.



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