Thyroid and Fertility: How Can Thyroid Function Affect Pregnancies in Couples?
Dr. Anish Musa
Dr. Anish MusaJanuary 19, 2023

Thyroid disorders can affect fertility in women and men.

Fertility defines the ability of a couple to conceive and carry the baby to term. That involves the role of both biological genders. The sperm quality and motility, as well as, the health of the ovaries and uterus impact conception.

Since all parts of the endocrine systems are connected they also influence the functioning of multiple organs and organ systems. The reproductive system is no exception. Thyroid and Fertility/

You may have already learned that hypothyroidism and hyperthyroidism affect menstrual cycles. That goes on to show that thyroid and fertility are deeply connected. Thyroid hormones affect the ovarian cycles and the window of fertility.

Today, we will find out how hypothyroidism and hyperthyroidism affect fertility in women and men.

How Do Thyroid Disorders Affect Fertility?

Thyroid disorders include hypothyroidism and hyperthyroidism. In hypothyroidism, the production of T3 and T4 hormones are lower than usual. In hyperthyroidism, there is an overproduction of T3 and T4 hormones. Both conditions influence fertility negatively.

When T3 and T4 are too low, TSH (Thyroid-stimulating hormone) levels are high. When T3 and T4 levels are high, TSH is low. Abnormal levels of TSH directly interfere with ovulation. Hypothyroidism and hyperthyroidism disrupt the ovulation cycle. Join Thyroid Community/

Common signs that your thyroid hormone levels are affecting your ovarian cycles –

  • Menstrual cycles that are longer or shorter than usual
  • Menstrual bleeding that’s heavier or lighter than typical
  • Periods that last longer or shorter than typical for you

The role of thyroid hormones in male reproduction and fertility is undisputed. However, to assess their fertility, tests such as sperm quality and motility are necessary.

What’s the Link Between Overactive Thyroid and Fertility?

Hyperthyroidism or overactive thyroid can disrupt the estrogen and progesterone levels in a woman’s body. The hormones directly affect the ability of a woman to conceive and carry a pregnancy to term.

Overactive Thyroid and Fertility before Pregnancy

Graves’ disease is the most common cause of overactive thyroid disease in both men and women. Thyroid and female fertility are closely linked. Seeking proper diagnosis and treatment for hyperthyroidism is absolutely necessary if you are planning to conceive. Thyroid and fertility problems in female patients are almost always treatable.

Talk to your functional medicine doc and OBGYN about your diagnosis before planning your pregnancy. The presence of Graves' antibodies can affect your and your baby's health. You need to get regular checkups before conceiving.

Do not stop medication for Graves’ disease or hyperthyroidism without consulting your endocrinologist and OBGYN.

The importance of thyroid hormones in male reproduction and fertility includes maintaining viable sperm count and motility. It can reduce fertility considerably. Ensure proper treatment for your hyperthyroidism since the sperm count may return to normal once hyperthyroidism medication begins.

Men who are on anti-thyroid drugs can still father a child without any risks.

Hyperthyroidism during Pregnancy

Untreated hyperthyroidism can increase the risks of a miscarriage during the early stages of pregnancy. Sadly, many antithyroid drugs to treat hyperthyroidism put the unborn baby at a higher risk of developmental abnormalities.

Since thyroid and fertility in female patients are interrelated, not treating hyperthyroidism before and after pregnancy can cause high blood pressure during pregnancy, premature birth, and poor growth of the baby.

If you have been taking Carbimazole (CMZ), you need to switch to Propylthiouracil (PTU) ASAP. During the first trimester, PTU is the drug of choice since it has minimal side effects. Studies have shown that CMZ increases the risk of birth defects in the fetus.

A higher than the necessary dose of anti-thyroid meds can cause hypothyroidism in the unborn baby. Hypothyroidism can lead to stunted growth and development of the child. It can permanently affect the child's brain development.

Active hyperthyroidism means you MUST take antithyroid medication during pregnancy. However, most antithyroid drugs cross the placenta. Therefore, you will have to talk to both your endocrinologist and OBGYN to find the lowest possible dose that works for you.

You should not rely on any form of Block and Replace therapy during your pregnancy. Block and Replace refers to the use of an anti-thyroid drug to completely block the thyroid function and replace the thyroid hormones with levothyroxine. It is effective in treating hyperthyroidism, but only when someone is not pregnant.

Thyroid surgery to manage hyperthyroidism is extremely rare during pregnancy. In case your hyperthyroidism isn’t responding to CMZ or PTU, you should speak to your endocrinologist about surgical interventions.

Although overactive thyroid and fertility are directly liked in women, no one should opt for radioactive thyroid treatment for hyperthyroidism during pregnancy.

The dangers of untreated hyperthyroidism during pregnancy are much higher than taking antithyroid drugs during pregnancy.

Hyperthyroidism after Delivery

Once you have a healthy child, your Graves’ disease may relapse. You should schedule thyroid blood tests complete with Graves’ antibody testing immediately after giving birth and then after every 3 months.

Never stop your antithyroid drugs after childbirth, unless your endocrinologist and OBGYN tell you to. You can continue to breastfeed even when on anti-thyroid drugs for hyperthyroidism. If you are still concerned, you can always talk to our functional medicine doctors for further guidance.

How does Underactive Thyroid Affect Fertility and Pregnancy?

Hypothyroidism or the lack of enough T3 and T4 hormones in the system. An underactive thyroid can lead to several health complications including a slow metabolism, rapid weight gain, low hemoglobin (anemia), and heart issues.

Low levels of T3 and T4 affect the levels of estrogen and progesterone directly. Therefore, hypothyroidism directly influences a woman’s ovarian cycles and menstrual cycles.

Hypothyroidism before Pregnancy

Untreated, underactive thyroid (hypothyroidism) can make it difficult for a couple to conceive. Women with hypothyroidism can have heavier and longer periods. It can cause them to become anemic. Anemia can cause a person’s periods to stop altogether. Proper treatment for hypothyroidism including levothyroxine can increase a woman’s chances of becoming pregnant. Hypothyroidism also affects fertility in men. Low thyroid hormones can influence sperm count and motility in men. However, once treatment for hypothyroidism begins, sperm quality should go back to normal (unless there are other underlying health issues).

While planning your pregnancy, do not forget to get your thyroid blood test completed. If you have high anti-thyroid peroxidase (TOP) antibodies, talk to your endocrinologist and OBGYN immediately. It is common among women who have thyroid autoimmunity.

Subclinical Hypothyroidism and Pregnancy

In some cases, the TSH concentrations are above the normal range. However, the free T4 remains in the normal range. Endocrinologists refer to this as subclinical hypothyroidism.

If your TSH is above normal, but free T4 is within the normal reference range, you may need levothyroxine during pregnancy. Studies show that modification of diets and lifestyle, along with the right supplement can help you reign in your subclinical hypothyroidism symptoms before pregnancy.

Hypothyroidism during Pregnancy

During the first 20 weeks of pregnancy, you may require higher doses of levothyroxine. That is because your baby will require thyroid hormones in optimal amounts as well.

If you are already taking levothyroxine, you should speak to your doctor about increasing your dose by 20 to 50 mcg depending on your thyroid hormone levels. You will need multiple thyroid tests every couple of weeks to ensure that your thyroid hormone levels are within the normal range.

During hypothyroidism treatment during pregnancy, you may require multiple dose adjustments. Do not forget your supplements containing calcium, iron, and folic acid during your pregnancy. Ensure that you take these several hours before taking the levothyroxine.

Hypothyroidism after Delivery

In the majority of the cases, women go back to their old dose of levothyroxine after giving birth. Before reverting to the old dose you should definitely get your thyroid blood tests. You will need to get the tests done immediately after birth, and a couple of days after that. Repeat the test as frequently as your endocrinologist advises.

It is critical to have your baby checked for hypothyroidism as well if you have had low T3 and T4 hormones during your pregnancy.

What Is Postpartum Thyroiditis?

5 to 10% of pregnancies result in postpartum thyroiditis. It is an inflammatory disorder of the thyroid gland. It's common among women with thyroid antibodies. Postpartum thyroiditis occurs between six and twelve months after childbirth.

Symptoms of postpartum thyroiditis include signs of hyperthyroidism that evolve into signs of hypothyroidism. For example –

  • Tedium
  • Lethargy
  • Depression
  • Low tolerance to col

Almost all women with advanced postpartum thyroiditis experience painless swelling of the thyroid gland.

You will need levothyroxine along with dietary modifications and lifestyle changes to bring your thyroid function back to normal. You may be able to maintain your thyroid hormone levels at a normal range after six to twelve months.

You may require a thyroid blood test every month to monitor your T3 and T4 levels once you have begun taking levothyroxine.

Winding Things Up

  1. If you have thyroid disease, speak to your endocrinologist, OBGYN, or functional medicine doctor before planning a pregnancy.
  2. Thyroid problems can contribute to fertility problems in men and women.
  3. Medication and treatment for thyroid hormones in male reproduction and fertility almost always restore sperm count and viability.
  4. If you have had thyroid treatment in the past, disclose all information to your OBGYN.
  5. If you have Graves' disease or Hashimoto's thyroiditis (auto-immune conditions), you will require frequent blood tests to determine the levels of T3 and T4 hormones.
  6. When taking antithyroid meds, speak to your endocrinologist about changing it or adjusting its dose before conceiving.
  7. When taking levothyroxine or something similar for hypothyroidism talk to your OBGYN for dose adjustment during pregnancy.

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