Understanding the link between your thyroid and fertility

Guest blog by Lesley O’Connor

Many people overlook the link between their thyroid and fertility. Low thyroid (hypothyroidism) dysfunction can disrupt the menstrual cycle and egg development, which impacts fertility and pregnancy.

There is also a higher prevalence of Hashimoto’s Thyroiditis (HT) in those with Polycystic Ovary Syndrome (PCOS) and Endometriosis, which can all impact fertility. Let's take a deeper look at what's happening and what you can do.

How does your thyroid affect your fertility?

It's important to understand that thyroid hormones not only indirectly affect the synthesis, secretion, and action of reproductive hormones, but are also regulated by these hormones at the same time.

There are four key areas where low thyroid function (hypothyroidism) can impact fertility. These include:

Hormone Health

  • Hypothyroidism can increase the hormone prolactin levels which can cause an irregular cycle

  • Hypothyroidism can lead to ovulatory dysfunction and inadequate progesterone production which is vital for getting pregnant

Egg Development

  • There are thyroid hormone receptors in the ovaries which are critical for correct egg development which is important for a healthy pregnancy

Conception

  • Low thyroid hormones can impact the correct endometrial receptivity and implantation of an embryo

  • Thyroid anti-bodies can negatively affect fertility independent of thyroid hormones

  • Long-term PCOS & Hashimoto's can contribute to the development of Premature Ovarian Insufficiency (POI) which makes it difficult to get pregnant

Miscarriage

  • Miscarriage, premature delivery, and stillbirths are common in hypothyroidism

  • Maternal thyroid needs to be sufficient for the first trimester to make hormones for both mother and baby

What can you do about your thyroid and fertility?

Nutrients, herbs, and lifestyle are important for both thyroid and fertility function. There are several cross-overs between interventions that can benefit both aspects of fertility and thyroid function.

Nutrients that help improve both thyroid function and fertility

Many nutrients that help thyroid health also improve fertility. This includes iodine, vitamin D, zinc, and selenium

Iodine

  • Iodine is important for thyroid hormone production

  • Ovaries have the second-greatest capacity for iodine uptake outside the thyroid, which is crucial for egg growth

  • Preconception commencement of iodine supplementation >150 mcg per day is associated with reduced time to conception

Vitamin D

  • Vitamin D is thought to influence both egg quality and endometrial receptivity

  • It's important for thyroid hormone production and conversion of T4 to T3

  • Preconception vitamin D levels >75 nmol/L are associated with better fertility outcomes

Zinc

  • Zinc is important for thyroid hormone production and conversion of T4 to T3

  • It improves egg development, fertilisation and implantation rates

  • Helps foetal and placental growth

Selenium

  • Selenium plays a role in iodine metabolism

  • It's important for thyroid hormone production and conversion of T4 to T3

  • Helps manage thyroid antibodies in Hashimoto's which reduces the risk of thyroid autoimmunity (TAI) related infertility.

  • Important antioxidant for egg quality especially in endometriosis

Herbs for Thyroid & fertility health

Western Herbal Medicine is a fantastic tool for both thyroid and sex hormones, as well as the immune system. Nigella Sativa, also known as Black Cumin is a fantastic herb for those with low thyroid function, as it helps reduce antibodies and improve thyroid function. This can, in turn, help to regulate the menstrual cycle. promote ovulation, and progesterone levels.

Herbs should always be prescribed by a qualified Naturopath or Herbalist.

Lifestyle

Small lifestyle changes add up fast for thyroid health and fertility. I recommend starting small and not aiming to be perfect about doing everything right 100% of the time.

  • Avoid endocrine-disrupting chemicals that negatively impact fertility and thyroid health

  • Drink filtered water

  • Manage stress by finding what relaxes you

  • Participate in regular physical activity, aiming for at least 150 minutes over the week

Wrapping up your thyroid and fertility

I recommend a full thyroid assessment, hormone panel, and nutrient testing at least 3 months prior to trying to conceive. This means that your thyroid and fertility can be optimal when you actively start trying to conceive.

About the Author

Lesley O’Connor is a Clinical Naturopath (BHSc) with a special interest in Women’s Health. This ranges from preconception through to menopause! Lesley helps support women with their fertility, energy, vitality, and metabolic health with the use of herbal medicine, nutrition, and lifestyle changes. Lesley runs an online Naturopathy clinic, lectures, and supervises final year Clinical Nutritionists before they graduate.