Hashimoto's Thyroiditis and PCOS: Is There a Connection?

With Trevor Angell, MD, and Mario Skugor, MD

The quick answer is yes. If you have been diagnosed with polycystic ovary syndrome, or PCOS, you are well aware that one the telltale sign is that your hormone levels are out of balance. Common symptoms include menstrual irregularity, problematic acne, and excessive hair growth. You may also struggle with your weight due to the disruptions that PCOS causes to your metabolism, and you may have difficulty getting pregnant.1  

As if that’s not enough, you are likely at higher risk for Hashimoto’s thyroiditis. A team of researchers from Germany examined the medical charts of 827 women with PCOS who were receiving care from an outpatient fertility clinic.2 These investigators were interested in learning more about the metabolic and reproductive problems commonly seen in these patients.     

Obesity and metabolic disturbances are common in autoimmune thyroiditis and polycystic ovary syndrome.

Hashimoto’s Thyroiditis is Common in Women with PCOS

According to their analysis, published in Experimental and Clinical Endocrinology & Diabetes,2 the researchers found that many women with polycystic ovary syndrome may also have problems with their thyroid, a gland that helps to maintain metabolic processes in the body.3

More specifically, this form of thyroid disease—Hashimoto’s thyroiditis, an autoimmune hypothyroid condition in which the body’s immune system attacks the thyroid—is three times more common in women with PCOS than in women without it.2

Besides assessing the prevalence of Hashimoto’s thyroid disease in women who have been diagnosed with PCOS, Jan Ulrich, MD, and his team also studied the impact that autoimmune thyroiditis may have on hormonal changes.2

If you are a woman with PCOS, your body may be producing too much androgen. Androgens are a class of male sex hormones, in particular, testosterone, that are found in smaller but necessary levels in women too.4 Higher levels of androgen may interfere with a woman’s ability to get pregnant; for this reason, many women with PCOS struggle with infertility.1

Surprisingly, the researchers found that high levels of androgen are less common in patients who have both conditions: Hashimoto’s thyroiditis and PCOS. This hormone pattern was confirmed even when looking at testosterone alone–an increased testosterone level is not found in patients with both conditions.2

Dr. Ulrich and his co-authors speculate that thyroid autoimmunity suppresses androgen production but they do not have a clear reason as to why it happens.2

Metabolic Complications Similar in PCOS and Thyroiditis

The researchers assessed the impact of having both Hashimoto’s thyroiditis and PCOS on weight gain and risk for obesity. They used body mass index (BMI), as one method of assessing weight goals.2 Your doctor will likely use this value to determine if you are within a healthy weight.In patients with both polycystic ovary syndrome and autoimmune thyroiditis, BMI is generally higher than patients with only one of these conditions or neither condition.2

Two endocrinology experts commented on this study: Trevor Angell, MD, a thyroid specialist practicing at Brigham & Women’s Hospital in Boston, Massachusetts, and an instructor of medicine at Harvard Medical School; and Mario Skugor, MD, chairman of endocrinology and metabolism and clinical assistant professor of medicine at Cleveland Clinic Lerner College of Medicine at Case Western Reserve University in Ohio.

Both experts had similar responses to the overall finding of the study, that is, that it is clear that Hashimoto’s thyroiditis occurs in many women who have PCOS. 

“An association between autoimmune thyroid disease and a polycystic ovary syndrome phenotype has been often – but not universally – found, so the suggestion of an increased prevalence of Hashimoto’s thyroiditis in patients with polycystic ovary syndrome is not surprising,” Dr. Angell tells EndocrineWeb. 

Dr. Skugor concurs. “The population studied comes from a fertility clinic, and since both conditions—PCOS and autoimmune thyroiditis—impair fertility, and it is more likely for both metabolic diseases, which have a genetic link, to be found in these patients,” he says. 

Managing Your Health when Diagnosed with Both Conditions

According to Dr. Urich and his team, their findings matter because the data comes from “the largest single cohort examined to date.”  Therefore, the results are of value, as they underscore the importance of screening women for autoimmune thyroiditis, especially in patients concerned about their fertility,2 according to the authors.

“In summary, a 3-fold increase in the prevalence of autoimmune thyroiditis, and hypothyroidism in women with PCOS appears to be established. And, the presence of both PCOS and Hashimoto’s thyroid disease seems to worsen the impact on metabolic, cardiovascular, and reproductive outcomes,”2 the authors wrote.2

So if you have polycystic ovary syndrome and are being evaluated for infertility, be sure ask your physician about your risk for comorbid conditions, in particular, Hashimoto’s (autoimmune) thyroiditis. 

According to the experts, patients seeking reproductive evaluations for difficulty in getting pregnant are often screened for both polycystic ovary syndrome and hypothyroid disease because of their known impact on sex hormones and fertility. 

“An important question for these women—does treatment with thyroid hormones improve fertility in women with autoimmune thyroiditis?” Dr. Skugor tells EndocrineWeb. He recommends directing future research to this issue, particularly as several studies suggest the value of thyroid hormone is beneficial during fertility treatment.5,6

“Additional studies are needed to elucidate how Hashimoto’s thyroiditis and PCOS are associated and the mechanisms connecting them,” Dr. Angell suggests. “Both PCOS and autoimmune hypothyroid disease have been associated with less successful fertility, and understanding the particular outcomes for patients with these conditions and the ideal treatment in these patients warrant further study.”  

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