January 31, 2024
6 Minutes

Will Low Thyroid Affect My Fertility?

Will Low Thyroid Affect My Fertility?
Written by
Navya Muralidhar
MSc Clinical Embryology & Embryologist
Amilis makes fertility digestible, accessible, and affordable to help you take charge of your reproductive health and live on your own timeline.

In an eggshell...

  1. Low thyroid levels can affect your fertility by altering the regularity of menstrual cycles, and even lowering your AMH levels.
  2. Generally- this doesn’t affect egg freezing. There are precautions taken to monitor, medicate, and bring down TSH to optimal levels during egg-freezing cycles.
  3. And yes, it’s completely possible to freeze eggs with hypothyroidism.

Fertility and Low Thyroid: Should I still freeze my eggs?

The thyroid gland is a butterfly-shaped organ near your neck, which releases the thyroid hormone. 

Its job description looks something like this: controlling your metabolism, how fast your heart beats, and how quickly you burn calories. It also affects your menstrual cycle and ovulation. 

So when is thyroid hormone produced? It’s when the pituitary gland, (the headquarters 🏛️of hormone production in the brain, releases TSH or thyroid-stimulating hormone). 

Here’s what happens:

But, sometimes, there can be hiccups.😵‍💫

Disturbances in the function of the thyroid gland can either lead to underproduction (hypothyroidism) or overproduction of hormones (hyperthyroidism). Either of these situations can interfere with how regular your periods are, your hormonal levels during your cycles, and egg release. 

So, is there any way to detect this? And if so, how exactly does it affect your choice of egg freezing?

What is hypothyroidism?

Hypothyroidism is where your thyroid gland is underactive , or produces less thyroid hormones. This could mean a slowdown in all body functions such as metabolism, and other activities affected by thyroid hormones. There’s also a milder version of it, known as subclinical hypothyroidism

In terms of values, hypothyroidism is where TSH values are higher than normal. For reference, if the normal range of TSH is 0.45 to 4.5 mIU/L, then, 

  1. Subclinical Hypothyroidism is where TSH > 4.5-10 mIU/L
  2. Hypothyroidism is where TSH > 10 mIU/L

How does thyroid function affect your fertility?

Among other things, such as regulating your metabolism, the thyroid gland also affects the production of two crucial hormones related to your fertility- FSH and LH. 

🤓Let’s nerd it out for a bit here.  

Remember, the follicle-stimulating hormone stimulates the follicles that produce mature eggs in the ovaries, and the luteinizing hormone helps regulate the menstrual cycle and ovulation. 

An imbalance in thyroid function or hormone production can directly affect the production of these hormones. Specifically, hypothyroidism leads to lower levels of FSH and LH.

This could mean- affected menstrual cycles, ovulation, and thereby an overall cause of fertility issues. 

Does low thyroid affect egg freezing?

Here’s the thing: Low thyroid hormone levels affect the hormones that naturally prepare your body to release an egg. But with egg freezing, you will be medicated based on your thyroid levels, which stimulates and controls the eggs produced for that cycle. So ideally, it shouldn’t affect your egg freezing cycle.

How exactly, you ask?

Normal thyroid hormone levels range from 0.45 to 4mIU/L. Now, in the case of low thyroid levels or hypothyroidism, the levels can either range from 4.5 to 10mIU/L (subclinical hypothyroidism) or over 10 mIU/L (primary hypothyroidism).

As per the international guidelines set by the American Society of Reproductive Medicine (ASRM), it is recommended to have TSH levels < 2.5 mIU/L. However, some studies mention how it’s better to have TSH levels at 4 mIU/L before undergoing egg freezing or IVF.

So, for patients who have hypothyroidism, where levels are over 4 mIU/L, there is medication suggested to reduce or maintain these levels at 4mIU/L. 

This is the prior monitoring and treatment in place that happens, before moving on to a cycle of egg freezing. Kind of like a shield, to avoid hypothyroidism from affecting your egg freezing process. 

So, low thyroid levels, at the most, can affect how they monitor your cycle, your medication, and its dosage during egg freezing. Along with this, your healthcare provider will inform you about maintaining the preferred levels of thyroid hormones before and after egg freezing.

Does TSH level affect egg quality?

As per a study, it was found that it wasn’t low TSH but rather, a higher TSH that affected egg quality. This is seen in hypothyroidism, where women have high TSH, but low thyroid hormone levels. 

Women with low TSH (hyperthyroidism) experienced issues related to ovulation and the regularity of their menstrual cycle, but women with higher TSH (hypothyroidism) were seen to have lower levels of AMH. 

AMH is a crucial hormone that plays a role in egg development, growing follicles, and the viability of eggs. A drop in this hormone can lead to lower follicle counts (aka the chances of lower egg quality and quantity).

Can thyroid cause low AMH?

This depends on the level of thyroid hormones. Studies have observed that people with higher thyroid levels and thyroid autoantibodies (a condition where cells in our own bodies attack thyroid cells) were found to have low AMH. Hence, there is a possibility of hypothyroidism causing low AMH.

Can a woman with thyroid problems get pregnant?

Yes, women with thyroid problems can conceive, but it often requires personalised treatment. Even during the process of egg freezing, or IVF, it’s advised to have the TSH levels below 2.5 mIU/L. During your treatment, it’s important to discuss with your doctor, get your thyroid levels tested, and opt for a personalised treatment plan that better aids your chances of success.

How Amilis can help with your egg-freezing journey

Understanding your thyroid levels and their connection to fertility doesn’t have to be a shushed matter anymore. If you’re considering egg freezing- we always recommend a thyroid test from our end- to ensure you the best treatment possible. 

While it’s not a mandate with all clinics, some offer thyroid tests as a part of the package, and some don’t. You can also head over to our clinic comparator to check clinics that offer a thyroid test before egg freezing.

Not there yet? We still got you. Amilis is out here to bridge the exact gap that you face between “I might want to freeze my eggs” and “How do I get started”. With the right resources, tests, and clinic suggestions in place, we’re all set to give you the right information, at the right time, to help you make informed decisions for yourself.

Written by
Navya Muralidhar
MSc Clinical Embryology & Embryologist

An embryologist by degree, and an educator by heart, Navya has completed her Bachelors in Genetics, and her Masters in Embryology and now strives to deconstruct the complex, into educational and informative articles surrounding her field of interest. She's specifically focused on time-lapse technology, IVM, and pre-implantation genetics. When not writing, you can find her at her favourite or newest coffee shop in town, sketching away, or listening to a podcast.