PCOS and hypothyroidism: Are thyroid issues related?

Hypothyroidism and polycystic ovary syndrome (PCOS) are two different conditions that can go hand in hand, but they are not necessarily cause and effect. PCOS is a complex endocrine condition in reproductive-age females, which manifests in a variety of symptoms where thyroid problems can be one of the additional issues. But how exactly is PCOS and thyroid related? Let’s see what experts and research have discovered so far.

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PCOS and thyroid connection

First of all, let’s define what is what.

The thyroid is a gland in the neck that secretes hormones. Its main role is to control metabolism, which is how your body transforms the food you consume into energy. The thyroid also plays a role in your period cycle health, although indirectly, by influencing the hypothalamic-pituitary-gonadal (HPG) axis.

When the thyroid is imbalanced, a person can develop disorders when the gland produces too little (hypothyroidism) or too much (hyperthyroidism) thyroid hormone. These disorders can affect not just metabolism but also energy level, bone health, and even menstruation issues. Hypothyroidism and hyperthyroidism can make periods very light, heavy, or irregular. 

Now, why is PCOS and thyroid discussed together?

During the last several years, several studies reported an increase in the number of thyroid disorder cases among women with PCOS. 

According to a study from 2011, thyroid dysfunctions were found to be more prevalent in women with PCOS, although ovarian disease itself has little to do with the risk of developing thyroid disease. In this study, PCOS alone was not associated with thyroid disease, but metabolic syndrome (MS), which is quite common for PCOS-affected women, was related to thyroid issues.

Another study from 2019 discovered that the risk of thyroid disease in women with PCOS is 2.5 times higher than that in women without PCOS. 

The reasons why and how exactly PCOS and thyroid issues can be related are still not defined. Currently, it is known that females are generally at higher risk of developing thyroid dysfunctions than males, and the older a person gets, the higher the risk for both sexes. In the reproductive years, thyroid disease prevalence is relatively low – around 4-6% in the general population. 

Experts don’t know how PCOS and thyroid issues are related, but consider the following factors as potential ones:

• Hormones. Both conditions are about hormonal imbalances, even though the affected hormones are completely different. PCOS involves reproductive hormone imbalances (androgens, estrogen, progesterone, and others), while thyroid disorders involve thyroid hormone dysfunction. Since a person's body is a complex mechanism where one issue can trigger or exacerbate another, these hormonal imbalances can worsen the symptoms.

• Insulin resistance. Hypothyroidism and PCOS are both associated with insulin resistance when the body doesn't respond properly to insulin. This shared feature can lead to similar metabolic problems like increased BMI (body mass index) and the risk of type 2 diabetes.

• Inflammation. Both conditions may be linked to chronic inflammation. This inflammatory process can contribute to the development of symptoms.

Hyperthyroidism or hypothyroidism in PCOS?

Hypothyroidism is an underactive thyroid that does not produce enough hormone, and hyperthyroidism is an overactive thyroid that produces too much hormone. Generally, hypothyroidism is more common than hyperthyroidism. 

For instance, several studies said that compared with hyperthyroidism, hypothyroidism is more common in PCOS patients.

Although these are two opposite sides of thyroid functioning and thus symptoms differ, some of these symptoms overlap.

Hypothyroidism symptoms

The underproduction of thyroid hormone can manifest in the following health issues:

• Tiredness and fatigue
• Constipation
• Dry skin
• Weight gain
• Puffy face
• Hoarse voice
• Coarse hair and skin, thinning hair
• Muscle weakness, aches, tenderness, and stiffness
• Slowed heart rate (bradycardia)
• Low mood or even depression
• Memory problems 
• Brain fog
• Heavy or frequent menstrual bleeding
• Infrequent or absent menstrual cycles

Hyperthyroidism symptoms

The excessive thyroid hormone production can be noticed by the following symptoms:

• Fast heartbeat (tachycardia) or irregular heartbeat (arrhythmia)
• Increased hunger
• Unintentional weight loss
• Nervousness, anxiety, and irritability
• Tremor, usually a small trembling in the hands and fingers
• Sweating and increased sensitivity to heat
• Enlarged thyroid gland
• Tiredness
• Muscle weakness
• Sleep problems
• Thinning skin
• Fine, brittle hair
• Absent or infrequent periods
• Light and short periods

How are thyroid issues tested and diagnosed?

There are several ways that thyroid health can be examined.

Blood test

Health care providers might recommend checking TSH (thyroid-stimulating hormone), T-4, and T-3 in a blood test. If the results show that TSH is high while T-4 and T-3 are low, then the diagnosis is hypothyroidism. With hyperthyroidism, on the contrary, TSH is low while T4 and T3 levels are high. What else can be tested besides TSH (thyroid-stimulating hormone):

• T3 or free T3 (tri-iodothyronine);
• T4 or free T4 (thyroxine);
• TPO (thyroid peroxidase antibodies), also known as microsomal antibodies;
• TG (thyroglobulin);
• TGAb (thyroglobulin antibodies);
• TSI (thyroid-stimulating immunoglobulin).

Ultrasound and scans

Thyroid imaging tests can show information about the size, shape, and function of the thyroid gland. This test can be recommended after thyroid blood tests for additional information. If scans show a lump on a neck, doctors may recommend a biopsy, known as FNA (fine needle aspiration), to see if the lump is noncancerous or cancerous.

Can PCOS cause thyroid issues?

Women with PCOS are indeed at higher risk of developing thyroid dysfunction, particularly hypothyroidism. However, PCOS itself is not exactly the cause. More research is needed to define the mechanisms behind this link, and the exact reasons why and how PCOS and thyroid dysfunction are related. If you have PCOS, it doesn’t necessarily mean that you have thyroid dysfunctions. For example, hyperthyroidism does not usually occur alongside PCOS, but hypothyroidism is more likely yes.

Generally, thyroid disorders are prevalent in 30% of PCOS-affected women. And hypothyroidism is almost three-fold more often observed in PCOS patients than hyperthyroidism.

Does PCOS cause hypothyroidism?

According to numerous studies, hypothyroidism is 11-14% more likely to occur in PCOS-affected women. Although PCOS is found to be linked to several issues, such as hypothyroidism and metabolic disorders, it’s not exactly causing it. However, the risk of developing thyroid dysfunction is higher if you have PCOS. In short, having PCOS may increase the risk of developing thyroid disease.

Does hypothyroidism cause PCOS?

The short answer is no, there is no evidence that primary hypothyroidism can lead to PCOS, and hypothyroidism itself doesn’t cause PCOS or increase the risk of it. However, hypothyroidism can affect the ovaries in a similar way as PCOS. Particularly, hypothyroidism can cause cysts and the enlargement of the ovaries. 

Thyroid disorders are exclusion criteria before PCOS diagnosis, and hypothyroidism or hypothyroidism are ruled out before diagnosing PCOS. This means that before diagnosing Polycystic Ovary Syndrome, doctors need to make sure the symptoms are not because of a thyroid problem. 

If someone has symptoms that could be either PCOS or a thyroid issue (like irregular periods), the health care providers will inspect the thyroid first. Only after ruling out thyroid dysfunction can they accurately diagnose PCOS.

PCOS and hypothyroidism symptoms in combination

PCOS and thyroid dysfunction both affect the endocrine system and hormonal balance. However, having PCOS doesn’t necessarily mean having thyroid issues, and having thyroid issues doesn’t necessarily mean having PCOS. 

But what if someone has been diagnosed with both PCOS and hypothyroidism? Basically, thyroid disorders like hypothyroidism tend to worsen PCOS symptoms and increase the risk of insulin resistance. 

Even though PCOS and hypothyroidism “attack” different hormones, symptoms can be quite similar for both conditions. PCOS is related to an imbalance in reproductive hormones, and hypothyroidism is an imbalance in thyroid hormones (produced less than needed). 

If you have both PCOS and hypothyroidism, the symptoms may be more severe in combination than in someone who only has one of those two conditions. For example, in some studies women with combined hypothyroidism and PCOS had higher BMI, fasting blood glucose, and cholesterol compared to those who only had hypothyroidism. 

How to manage both PCOS and thyroid issues?

In general, experts suggest that lifestyle changes, metformin, and vitamin D seem to improve thyroid function. 

One of the most recommended treatments for both PCOS and hypothyroidism for most people is diet and nutrition. 

The British Thyroid Association suggests iodine and selenium for thyroid dysfunction and PCOS management. However, the dosage and forms in which these elements can be consumed shall be prescribed by a doctor. The excessive intake can be dangerous for health.

Hyperthyroidism can be cured in some cases, but hypothyroidism is not – it’s only manageable.

It is not possible to prevent hypothyroidism or hyperthyroidism. However, there is an exception: if an underactive thyroid is caused by iodine deficiency, an iodine supplement can help prevent hypothyroidism. 

Takeaway

Women with PCOS are more likely to have thyroid disorders (hypothyroidism particularly) than women without PCOS. The reason why is still unknown.

Hypothyroidism itself doesn’t cause PCOS and doesn’t increase the risk of PCOS, but having PCOS may increase the risk of thyroid issues.

The symptoms can be more severe in females who have both PCOS and thyroid problems. Currently, there's no cure neither for hypothyroidism nor for PCOS. However, it is possible to successfully manage the symptoms of both conditions.