Thyroid function links to the hormones involved in fertility, such as estrogen, progesterone, and testosterone. An overactive thyroid, which doctors call hyperthyroidism, can also directly affect the ovaries, impacting fertility.

Hyperthyroidism can lead to infertility. However, the link between the thyroid and reproductive function is complex.

Usually, treatment can successfully improve fertility in those with hyperthyroidism. However, some treatments may lead to hypothyroidism, or an underactive thyroid.

This article examines hyperthyroidism and infertility, the menstrual cycle, and getting pregnant with hyperthyroidism. It also covers diagnosis, fertility treatments, and more.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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Yes, hyperthyroidism can cause infertility. Doctors can usually reverse infertility once treatment restores healthy levels of thyroid hormone.

Due to limited data, experts do not know the extent to which hyperthyroidism is involved in fertility.

However, thyroid hormones are essential for the proper functioning of the female reproductive system, as they regulate the development and metabolism of the placental, uterine, and ovarian tissues.

Research has found that thyroid dysfunction plays a major role in the loss of fertility and can contribute to the following:

Learn about the differences between hyperthyroidism and hypothyroidism here.

Many people with hyperthyroidism experience menstrual disturbances.

Earlier research suggests that 65% of people with hyperthyroidism experience problems with their menstrual cycle. However, more recent data indicates that around 22% of people with hyperthyroidism experience menstrual disturbances.

According to other research from India, people with hyperthyroidism have lighter and more irregular periods.

This is because hyperthyroidism causes the liver to produce more sex hormone-binding globulin (SHBG) protein. Increased SBHG levels can lead to irregular periods and infertility.

Hyperthyroidism also causes increased production of the hormone prolactin. High prolactin levels can prevent the ovaries from releasing eggs, preventing fertilization.

This can cause menstrual disturbances and infertility.

Learn more about hyperthyroidism and the menstrual cycle here.

Although a person can become pregnant while they have hyperthyroidism, the disorder can make conceiving more challenging and lower pregnancy chances.

A 2018 review indicates that 5.8% of women with hyperthyroidism have primary infertility, which means they cannot conceive for the first time. It also states that 2.1% of women with hyperthyroidism have secondary infertility, which means they cannot conceive after having been pregnant at least once before.

A person can increase their chances of getting pregnant by getting treatment for hyperthyroidism.

Learn more about hyperthyroidism and pregnancy here.

Medication for hyperthyroidism typically consists of antithyroid medications and beta-blockers.

During pregnancy, a doctor may suggest a person avoid an antithyroid medication called methimazole during the first 3 months of pregnancy. They will likely prescribe a medication called propylthiouracil instead.

A person should not stop treating hyperthyroidism if they become pregnant. While mild hyperthyroidism is not typically problematic during pregnancy, severe cases can harm the pregnant person and baby if left untreated.

Radioactive iodine and conceiving

Radioiodine treatment involves taking radioactive iodine capsules or liquid orally, which destroys the thyroid cells that produce thyroid hormone.

Radioiodine therapy may contribute to delayed pregnancy, irregular menstrual cycles, and early menopause.

Doctors typically suggest that people who receive this treatment avoid getting pregnant for 6–12 months, as there is a risk of radiation to the eggs in the ovaries.

Learn more about nuclear medicine here.

Someone with hyperthyroidism symptoms should contact a doctor, as leaving the condition untreated can result in severe complications.

Symptoms of hyperthyroidism include:

To diagnose hyperthyroidism, a doctor may:

  • perform a physical exam
  • ask the person for their medical history
  • perform thyroid tests, such as a TSH, T3, and T4 test
  • administer imaging tests, such as a thyroid ultrasound and a radioactive iodine uptake test

To diagnose infertility in females, a doctor may:

  • Ask the person about their medical and reproductive history.
  • Carry out a physical exam, pelvic exam, and Pap smear.
  • Order blood tests to measure hormone levels.
  • Perform a laparoscopy, which involves inserting a small viewing instrument into an incision in the abdomen to examine the reproductive organs.
  • Order a hysterosalpingogram (HSG) to examine the fallopian tubes.
  • Perform a transvaginal ultrasound, which involves inserting an ultrasound wand inside the vagina that provides sound waves to produce an image of the uterus and ovaries.

Learn more about blocked fallopian tubes, diagnosis, and treatment here.

To treat infertility related to hyperthyroidism, doctors will treat the underlying hyperthyroidism. Once hormone levels have returned to acceptable levels, doctors may be able to reverse infertility.

Treatments include:

  • Medication: A doctor may prescribe medication, including beta-blockers or antithyroid medication, which cause the thyroid to produce less thyroid hormone.
  • Surgery: A surgeon may remove part of the thyroid, which can cause thyroid hormone levels to return to healthy levels.

Learn more about removing the thyroid gland here.

Doctors can typically treat hyperthyroidism effectively and reverse infertility caused by the disorder.

However, the outlook depends on the cause of hyperthyroidism. If the cause is Graves’ disease, a person may require ongoing treatment to manage their condition.

Radioiodine therapy may lead to hypothyroidism, which is an underactive thyroid. Hypothyroidism may also contribute to infertility. However, hypothyroidism is easier to treat with medication than hyperthyroidism.

A person may help prevent hyperthyroidism in various ways, which include:

  • stopping smoking
  • drinking less alcohol
  • avoiding consumption of iodine in certain foods, such as seaweed, supplements, and medication, including cough syrup, which may cause or worsen hyperthyroidism

Learn about the foods to eat and avoid with hyperthyroidism here.

This section answers some frequently asked questions about hyperthyroidism and fertility.

How common is infertility with hyperthyroidism?

According to a 2018 article, 5.8% of females with hyperthyroidism have difficulty conceiving for the first time, and 2.1% who have been pregnant at least once may find it difficult to conceive again.

Can thyroid medication help you get pregnant?

Treatment for hyperthyroidism can restore hormones to their usual levels. This could increase a person’s chances of becoming pregnant if their infertility was related to an overactive thyroid.

However, someone who is pregnant or planning to become pregnant should avoid some thyroid medications, including radioactive iodine and methimazole.

If a person with hyperthyroidism becomes pregnant or plans to become pregnant, they should discuss the appropriate medications with a doctor.

Can I get pregnant without a thyroid?

A person can get pregnant without a thyroid gland as long as they take adequate amounts of thyroid hormone replacement medications.

Hyperthyroidism can lead to elevated levels of the protein SHBG and the hormone prolactin, which can prevent the ovaries from releasing eggs.

This can lead to infertility and other reproduction-related problems, including loss of pregnancy, menstrual disruptions, and preeclampsia.

Treatment for hyperthyroidism can typically reverse infertility related to the condition. A doctor may suggest a person avoid certain thyroid medications and treatments, such as radioiodine therapy, if they are trying to conceive.