Healthcare provider with patient explaining the connection between PCOS and hypothyroidism

PCOS and Hypothyroidism: What's the Connection?

Medically reviewed on Sept 20, 2023 by Jillian Foglesong Stabile, MD, FAAFP. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Table of contents

People who experience unexplained weight gain, irregular periods, and abnormal hair growth can likely contribute their symptoms to a disruption in their endocrine system. This system is a hormone powerhouse. When functioning properly, it helps to regulate growth, reproduction, metabolism, and blood sugar levels. [1]

Polycystic ovary syndrome (PCOS), an endocrine disease, affects 15–20% of people assigned female at birth who are of reproductive age. People with PCOS will experience irregular menstrual cycles, elevated male hormones, skin problems, and, sometimes, infertility. [2] Similarly, hypothyroidism is an endocrine disorder that occurs when the thyroid gland under produces hormones critical to metabolism, slowing down the function of various organs. [3]

The link between polycystic ovary syndrome (PCOS) and hypothyroidism lies in their impact on fertility and origin in insulin resistance, as well as their overlap in symptoms. Mainly, irregular menstrual cycles, obesity, fatigue, low moods, and hair loss. It's also not uncommon for individuals to have both polycystic ovarian syndrome and hypothyroidism. [2]

Understanding PCOS In-Depth

When people assigned female at birth enter their reproductive years, they’ll experience monthly periods in which the uterine lining sheds, preparing the body for pregnancy. Normally, a complex interaction of hormones, produced in the pituitary gland and ovaries, regulates the menstrual cycle. These include [4]:

  • Luteinizing hormone
  • Follicle-stimulating hormone
  • Estrogen
  • Progesterone

Polycystic ovarian syndrome occurs when the body produces too many male sex hormones and too little female sex hormones. When the body doesn’t make enough of the luteinizing hormone, it can prevent the ovary from releasing a mature egg for fertilization (ovulation). As a result, small fluid-filled sacs can form in the ovaries. Although, this isn’t always the case. [5]

If ovarian cysts do form, they produce male hormones called androgens, which include testosterone and dihydrotestosterone. These hormones give people assigned male at birth their “male” characteristics, such as [6]:

  • Deepening of the voice
  • Hair growth
  • Sperm development

In healthy female bodies, the aromatase enzyme converts androgens into estrogen to regulate menstruation, support conception, minimize bone loss, and stimulate underarm and pubic hair growth. However, decreased enzyme activity can inhibit this process. [6] And, in people assigned female at birth, elevated androgen levels can disrupt the menstrual cycle. [5]

In addition to a hormonal imbalance, insulin resistance and obesity can also elevate androgen levels in the body. Consequently, the most common symptoms of PCOS patients include [5]:

  • Missed periods
  • Irregular periods
  • Light periods
  • Ovarian cysts
  • Excess body hair
  • Weight gain and/or obesity
  • Acne
  • Oily skin
  • Male-pattern baldness
  • Hair thinning
  • Infertility
  • Skin tags
  • Dark and/or thick skin patches

PCOS can also impact various metabolic processes throughout the body, which can increase the risk of [2]:

  • Impaired glucose tolerance
  • Prediabetes
  • Type 2 diabetes
  • Metabolic syndrome
  • Cardiovascular diseases, like hypertension and hyperlipidemia

When diagnosing PCOS, healthcare providers will look for at least two indicators of the disease [2]:

  • Irregular or infrequent periods (oligo/anovulation)
  • High levels of androgens (hyperandrogenism)
  • Polycystic ovaries, via ultrasound

If healthcare providers do identify PCOS, possible treatment plans include [5]:

  • Lifestyle changes, such as a healthy diet and exercise
  • Ovulation-inducing medications for patients seeking pregnancy
  • Birth control pills
  • Diabetes medication

Understanding Hypothyroidism In-Depth

It’s somewhat common for people with PCOS to also have hypothyroidism. In fact, 10–15% of people diagnosed with PCOS also experience thyroid disorders. Further, women are more likely to develop hypothyroidism, compared to men. [2,7]

The thyroid is a small butterfly-shaped gland found in the necks of both men and women. When the pituitary gland releases the thyroid-stimulating hormone, the thyroid itself releases its own hormones, which control metabolism. [2]

Essentially adequate levels of the thyroid hormone help to maintain healthy weight, energy, and internal temperature levels. Thyroid hormone also supports hair, nail, and skin growth, as well as brain development.

In some cases, the thyroid produces insufficient levels of the thyroid hormone. This is what’s called hypothyroidism. An underactive thyroid can contribute to high cholesterol, as well as [7]:

  • Fatigue
  • Weight gain
  • Intolerance to cold temperatures
  • Joint and muscle pain
  • Dry skin
  • Thinning hair
  • Irregular menstrual periods
  • Heavy periods
  • Fertility problems
  • Slowed heart rate
  • Depression

The causes of hypothyroidism are numerous, and include [7]:

  • Hashimoto’s disease – As the most common cause of hypothyroidism, Hashimoto’s disease occurs when the immune system attacks the thyroid. To defend itself, the thyroid becomes inflamed and, consequently, cannot make a sufficient amount of the thyroid hormone. The autoimmune disease can lead to fatigue, muscle weakness, weight gain, depression, and changes in hair and skin dryness and strength.
  • Thyroiditis – Thyroiditis, or the inflammation of your thyroid, can cause the thyroid hormone to leak from the gland. Initially, a surplus of the thyroid hormone will enter the bloodstream, causing thyrotoxicosis. This thyroid disorder can last for a few months. Once the hormone exits the bloodstream, however, thyroid hormone levels significantly decrease throughout the body and the thyroid becomes inactive. As a result, many people with thyroiditis require hormone replacement therapy.
  • Congenital hypothyroidism – Congenital hypothyroidism occurs in infants and is present at birth. Many times, the thyroid is not fully developed. Other times, thyroid function simply doesn't work properly. Consequently, babies with congenital hypothyroidism may also experience intellectual disabilities and growth disorders, since the thyroid hormone plays a critical role in brain development and growth. Fortunately, there are treatment options. Congenital hypothyroidism may be a life-long condition, but some children will outgrow it.
  • Thyroidectomy – Oftentimes, healthcare providers will remove the thyroid completely or partially to treat hypothyroidism, as well as goiters, thyroid nodules, and thyroid cancers. Naturally, the removal of the thyroid will inhibit the production of the thyroid hormone. To maintain normal body function, a healthcare provider will prescribe hormone replacement therapy.
  • Radiation treatment of the thyroid – Healthcare providers may treat hyperthyroidism (an overactive thyroid gland) with radioactive iodine. However, in most cases, this form of treatment will cause hypothyroidism, particularly if the treatment damages the thyroid.
  • Medications – Medications for heart problems, bipolar disorder, and certain cancers may disrupt hormone production throughout the body, typically by damaging the pituitary gland.

Since underactive thyroid symptoms overlap with many other diseases, like PCOS, diagnosis involves conducting blood tests that measure thyroid hormone levels in the body. To treat an underactive thyroid, patients receive hormone replacement pills—most commonly, levothyroxine—to increase hormone levels and regain homeostasis. [7]

Everlywell Thyroid Health Support Virtual Care

The Connection Between PCOS and Hypothyroidism

PCOS and hypothyroidism—more specifically, Hashimoto’s (HT) disease—may develop in a similar manner. Firstly, some patients are genetically predisposed to these endocrine disorders. Secondly, both PCOS and Hashimoto’s disease involve some level of inflammation and autoimmunity:

  • In PCOS, chronic low-grade inflammation and insulin resistance are common features
  • In HT, the autoimmune response against the thyroid gland leads to inflammation and damage [2]

Additionally, both PCOS and thyroid disorders impact metabolism and cardiovascular function negatively. Insulin resistance is also common in women with both or either disorders. In fact, a review found that a large number of PCOS patients have insulin resistance (70–80% of obese women with PCOS and 20–25% of lean women with PCOS), which can develop from [2]:

  • Thyroid dysfunction
  • Hyperandrogenism
  • Obesity
  • Increase in free fatty acids
  • Increase in cholesterol

Similarly, insulin resistance is more common in patients with a thyroid disorder, compared to those without. Studies also found that hypothyroidism in women with PCOS can lead to a higher risk of developing diabetes. [2]

A 2016 study on 100 women with PCOS also found that women with both PCOS and hypothyroidism had altered levels of lipids (fats) in their blood, specifically their serum lipid levels. This suggests that their cholesterol and triglyceride levels were not within the normal range, which is a known risk factor for cardiovascular problems. [2]

Further, infertility can be linked to both conditions. A 2013 study revealed that 50% of women with both PCOS and hypothyroidism experienced infertility, although researchers are uncertain of the exact cause. Fortunately, it was found that losing 5–10% of one’s body weight did improve ovulation. [2]

Make the Right Connections With Everlywell

The link between PCOS and hypothyroidism is complex. Generally, both conditions result from dysregulation within the endocrine system, in turn, causing hormonal imbalances. Similarly, it’s believed that the pathogenesis of both disorders may be genetic and/or related to autoimmunity.

Both PCOS and hypothyroidism can also impact the body in similar ways. Namely, insulin resistance may be prevalent, as well as increased cholesterol levels, which puts patients at a higher risk of diabetes and cardiovascular issues. The disorders may manifest in the same symptoms, too, causing weight gain, irregular menstruation, infertility, and mood changes.

To monitor your health and maintain optimal wellness, seek the assistance of Everlywell. Our at-home Thyroid Test measures three main thyroid hormones: TSH, Free T3, and Free T4, as well as thyroid antibodies. When you ship your sample to one of our CLIA-certified, third-party labs, you’ll receive a personalized report with actionable next steps.

Everlywell’s convenient at-home female hormone test also provides a comprehensive hormone panel, measuring for 11 biomarkers, including estradiol, progesterone, luteinizing hormone, follicle-stimulating hormone, and the thyroid hormone. If the test finds abnormal hormone levels, we’ll connect you with a board-certified healthcare provider to review your results through a secure platform.

Prioritize your health and wellness with Everlywell today.

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  1. Overview of the Endocrine System. EPA. Published March 13, 2023. URL. Accessed September 12, 2023.
  2. Peddemul A, et al. Influence of Subclinical Hypothyroidism on Women With Polycystic Ovary Syndrome: A Literature Review. Cureus. Published August 27, 2022. URL. Accessed September 12, 2023.
  3. Hypothyroidism (Underactive Thyroid). NIH. URL. Accessed September 12, 2023.
  4. McLaughlin J. Menstrual Cycle. Merck Manual. Published April 2022. URL. Accessed September 12, 2023.
  5. Polycystic Ovary Syndrome (PCOS). Johns Hopkins Medicine. URL. Accessed September 12, 2023.
  6. Androgens. Cleveland Clinic. Published October 24, 2021. URL. Accessed September 12, 2023.
  7. Hypothyroidism (Underactive Thyroid). NIH. URL. Accessed September 12, 2023.
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