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.
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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. 
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.  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. 
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. 
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 :
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. 
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 :
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.  And, in people assigned female at birth, elevated androgen levels can disrupt the menstrual cycle. 
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 :
PCOS can also impact various metabolic processes throughout the body, which can increase the risk of :
When diagnosing PCOS, healthcare providers will look for at least two indicators of the disease :
If healthcare providers do identify PCOS, possible treatment plans include :
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. 
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 :
The causes of hypothyroidism are numerous, and include :
Since hypothyroidism 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. 
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:
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 :
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. 
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. 
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. 
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 Women’s Health 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.