Does an Underactive Thyroid Cause your PCOS Symptoms?

PCOS and Thyroid

An underfunctioning thyroid, which is known as hypothyroidism, does not cause PCOS, there are, however, multiple correlations that are vital to know about.

In this blog post we will discuss how thyroid disease can mimic PCOS, how PCOS can affect thyroid hormones and vice versa, and what you can do to support your thyroid to function optimally.


Getting the Right PCOS Diagnosis

In many cases PCOS (Polycystic Ovarian Syndrome) is not easy to diagnose. Doctors either quickly dismiss a patient telling them that everything is okay without any further testing or express a PCOS diagnosis right away, without doing the testing required for confirmation of the syndrome.

A PCOS diagnosis is usually based on the 3 Rotterdam criteria. They include elevated levels of male hormones, such as testosterone, polycystic ovaries and irregular or absent periods due to a lack of ovulation. A woman should have at least 2 out of these 3 symptoms to be diagnosed with PCOS. In order to confirm a diagnosis, various other conditions such as a congenital adrenal disease or hypothyroidism have to be ruled out.


Hypothyroidism Can Mimic PCOS Symptoms

Hypothyroidism is one one the conditions that needs to be ruled out when PCOS is properly diagnosed. Why is that? Interestingly, hypothyroidism, which is an underfunctioning thyroid, can mimic many of the PCOS symptoms.



When the thyroid is underactive, it secretes less thyroid hormones. Adequate amounts of thyroid hormones are required to ensure the maturation of a handful of egg follicles each month. If thyroid hormone is low, those follicles may not fully mature and will stay inside the ovary for up to 3 months until they dissolve on their own. Increased ovarian volume is a common symptom of hypothyroidism.



If the follicles don’t mature, there won’t be a dominant follicle that will release an egg. When that is the case, ovulation does not happen, leading to irregular or absent periods.

Another overlap with PCOS are elevated prolactin levels, which, just like the fertility hormones LH and FSH, is secreted from the pituitary gland inside the brain. If prolactin is high, LH and FSH don’t receive the proper signaling to be secreted. If the ovaries don’t receive enough of these vital hormones, the maturation and release process of the follicles is interrupted and ovulation won’t take place.



It’s very common for women with PCOS to either have missing or irregular periods or suffer from heavy bleeding, due to estrogen dominance. Hypothyroidism can further aggravate or lead to estrogen dominance causing pelvic pain and heavy bleeding.


The Connection Between PCOS and Low Thyroid

PCOS and hypothyroidism interfere with each other in many ways. Let’s have a closer look at 3 factors: The auto-immune condition Hashimoto’s thyroiditis, elevated estrogen levels and blood sugar imbalances.



The most common cause for low thyroid in women with PCOS is the burned-out phase of Hashimotos’s thyroiditis, an auto-immune condition named after the Japanese specialist who discovered it in 1912. The prevalence of Hashimoto’s in women with PCOS lies at around 40%! So, make sure you get proper testing done, cyster! It’s much more common in women with PCOS than in the general population.

There is a clear correlation between Hashimoto’s and PCOS. With this disease, your body’s own immune system attacks the thyroid gland, causing inflammation and an overproduction of thyroid hormones. This is followed by underproduction of the thyroid hormones. Many women have “flares” of increased immune attack.

It is diagnosed with a blood test to check for antibodies against the thyroid, thyroid peroxidase antibodies (TPA), and anti-thyroglobulin anti-bodies (TGA).

Hashimoto’s usually progresses slowly over the course of many years. The burnout stage is reached when your thyroid produces inadequate amounts of thyroid hormone. Auto-immune disease is rooted in gut issues such as leaky gut and imbalances in your gut microbiome.


PCOS and Hashimoto's



Besides mimicking PCOS symptoms, an underlying thyroid condition can drastically impact estrogen levels. For example: hypothyroidism causes the liver to produce less sex-hormone-binding globulin, SHBG in short, which leads to higher amounts of free-circulation estrogen inside the blood stream.

Hypothyroidism also diminishes the body’s ability to accurately metabolize estrogen. This creates an environment that can lead to heavier periods, mostly in women with PCOS who are ovulating or are experiencing strong break-through bleeding from time to time.

As you can see, thyroid malfunctioning affects estrogen levels, but it also works the other way around: high amounts of estrogen negatively impact the thyroid by causing the liver to produce excess amounts of TBG, which stands for thyroid-binding globulin. TBG binds to thyroid hormone, preventing it from being used effectively inside the body.

Estrogen dominance can also worsen inflammation inside the body, which can further aggravate thyroid disease.



Next, let’s examine the connection between thyroid hormone and insulin more closely. As you already know, insulin resistance, which is characterized by high levels of insulin inside the blood stream, is very common in women with PCOS.

Hypothyroidism can worsen insulin resistance by making the cells less sensitive to insulin.

The connection between thyroid hormones and insulin goes both ways. Insulin resistance directly impacts thyroid hormone conversion. It leads to lower levels of active thyroid hormone.

This interplay gets a vicious cycle of exhaustion, weight gain, insulin resistance and hormonal imbalance going.


3 Ways to Support your Thyroid

So, what can yo do to support your thyroid? First of all, I would get proper testing done. Doctors usually only test TSH, but a full thyroid panel should include TSH, T4, T3, free T4, free T3, reverse T3, and the anti-body tests including TPA and TGA.

Unfortunately, if you’ve got the auto-immune disease Hashimoto’s thyroiditis, where the immune system attacks and destroys healthy thyroid tissue, your thyroid may be damaged to varying degrees. If the damage is severe, you might be dependent on thyroid medication for the rest of your life. Nevertheless, the tips outlined below, will help support your thyroid function.



Imbalances in the gut microbiome (the good and bad bugs inside your intestine) can aggravate auto-immune diseases. To support your gut, cut down on refined sugar and carbs, add probiotic-rich foods into your diet like coconut kefir, sauerkraut, kimshi or fermented pickles. Take a soil-based probiotic supplement.

Gluten leads to the secretion of the hormone zonulin, which can cause your intestinal walls to become leaky. Toxins, bacteria and undigested food particles can easily pass through the gut lining, which is only one cell layer thick. This activates the immune system on the other side leading to increased inflammation and can worsen auto-immunity. If you’ve got Hashimoto’s thyroiditis, cutting out gluten is highly recommended.



The thyroid needs adequate amounts of certain nutrients to function optimally. These include iodine, which is found in sea weed, milk, shell fish and salmon. Your body needs selenium to convert adequate amounts of thyroid hormone. Brazil nuts are a great natural source of selenium. Eat one or two Brazil nuts daily, preferably organic.

It’s also important to eat enough food. If you under eat or cut too many carbohydrates from your diet, which is the case on a keto diet, for example, you enter starvation mode, which lowers the conversion of thyroid hormone into its active form and thus slows down your metabolism.



One of the best ways to reduce estrogen levels is by eating a diet that favors blood sugar balance and thus prevent excessive secretion of the hormone insulin. High insulin levels activate an enzyme called aromatase inside the fat cells, which convert testosterone into estrogen.

Xenoestrogens, which are basically toxins found in plastic and personal care products, can mimic estrogen and dock unto estrogen receptors putting the body in a state of estrogen dominance. Try to avoid drinking from plastic bottles and buying canned produce. Use clean personal care products and household cleaners.

And lastly, try to reduce stress as much as possible. There are myriads of ways to do that: Go for long walks, connect with loved ones, do yoga or deep belly breathing.



So, to summarize, there are many correlations between PCOS and hypothyroidism. An underfunctioning thyroid can worsen PCOS and vice versa. The most common cause for hypothyroidism in women with PCOS is Hashimoto’s thyroiditis.

Dietary and lifestyle shifts, such as eating enough food and stress management can help support the thyroid and thus help improve PCOS symptoms.

I hope this article is helpful to you.

Feel free to ask any questions or leave a comment below.


Nadine xx

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