Women with PCOS have Increased Risk of Developing Hashimoto's Thyroiditis

Hashimoto's disease (autoimmune thyroiditis) worsens reproductive and metabolic outcomes in patients with polycystic ovary syndrome.

With Trevor Angell, MD, and Mario Skugor, MD

Researchers from Germany introduced evidence suggesting a threefold increase in the prevalence of Hashimoto's thyroiditis in women with polycystic ovary syndrome (PCOS) as compared to rates of this condition in the general population.1 Although other investigators have reported similar results,2-5 this study comprises “the largest single cohort examined to date,” according to the researchers who did not respond to a request for comments from EndocrineWeb.

Polycystic ovarian syndrome is a heterogeneous endocrine disorder affecting approximately 6 to 8% of reproductive-age women. Nearly half of patients with a diagnosis of polycystic ovary syndrome experience infertility,6 and up to one-third have obesity.7  Reproductive, metabolic, and physiological problems (such as those involving hair and skin) are frequent complaints in women with PCOS.8

Since the presence of Hashimoto's disease may exert negative effects on reproductive and metabolic parameters in women with PCOS, a better understanding of the impact of these comorbidities on these patients was warranted, according to the researchers. 

Hashimoto's thyroiditis occurs more often in women with polycystic ovary syndrome.

Analysis of Cohort with Comorbid Autoimmune Thyroiditis and PCOS

To examine the potential clinical implications of Hashimoto's thyroiditis in women with polycystic ovary syndrome, Jan Ulrich, MD, and his colleagues conducted a retrospective cohort study in which they evaluated data from the medical records of 827 women with PCOS who were receiving routine care at an ambulatory fertility clinic.1

Some women with both Hashimoto's disease and polycystic ovary syndrome have been found to experience greater metabolic disturbances,1 according to findings published in Experimental and Clinical Endocrinology & Diabetes. Yet, the study yielded some good news for these women—hyperandrogenemia and hyperandrogenism were less severe. 

The prevalence of Hashimoto's thyroid disease women co-presenting with PCOS was assessed in comparison to women without PCOS or ovarian disease who had undergone intracytoplasmic sperm injection for fertility treatment.1  Laboratory testing and thyroid ultrasound were used to diagnose Hashimoto's thyroiditis in study participants. The effect of Hashimoto's disease on PCOS was assessed through measurement of several reproductive and metabolic parameters, including body mass index (BMI), testosterone, sex hormone-binding globulin, free androgen index, estrogen, progesterone, 17-hydroxyprogesterone, follicle stimulating hormone, luteinizing hormone, and prolactin. 

Impact of Outcomes  on Comorbid Thyroiditis and Polycystic Ovary Syndrome

Patients with both conditions had a lower prevalence of hyperandrogenemia (66% vs 78%; P < 0.001) in comparison to patients with only PCOS.1 Although autoimmune thyroiditis may lead to menstrual cycle and/or ovarian cyst abnormalities that might, in turn, affect androgen production, neither was observed in this study cohort; thus, the investigators instead proposed that thyroid autoimmunity suppresses androgen levels. 

In addition, a lower prevalence of elevated testosterone (45 vs 61%; P < 0.001) and free androgen index (60 vs 67%; P = 0.09) was documented in patients with both diseases versus PCOS alone.1 Comorbidity also appeared to promote an increased BMI of 2 kg/m2 among women with both disorders.

In their report, the researchers explained that the more potent effect of autoimmune thyroiditis on testosterone versus free androgen index was likely due to the increased BMI. Sex hormone-binding globulin concentrations were decreased in those with a higher BMI; therefore, free androgen index appeared comparatively higher in patients with both conditions.1

The research team also documented a correlation between BMI and thyroid stimulating hormone (TSH) levels.1 BMI may be a “modifier of the Hashimoto's disease-risk,” based on our findings, according to the authors. However, while pediatric obesity also has been associated with increased TSH levels that decrease with weight loss, a causal relationship has not yet been confirmed.   

A Critical Review of the Study Findings

Two experts in this field were approached by EndocrineWeb to review this study: Trevor Angell, MD, a physician and thyroid specialist practicing at Brigham & Women’s Hospital in Boston, Massachusetts, and instructor of medicine at Harvard University; and Mario Skugor, MD, chairman of Endocrinology and Metabolism at Cleveland Clinic and clinical assistant professor of medicine at Cleveland Clinic Lerner College of Medicine of Case Western Reserve University.

Neither expert was surprised about the overall finding of the study, that is, that Hashimoto's thyroid disease is more common in women with PCOS than women without it.  “An association between auto-immune thyroid disease and polycystic ovary phenotype has been often – but not universally – found,” Dr. Angell explained to EndocrineWeb. 

Dr. Skugor concurred, noting that “[t]he population in this study is from a fertility clinic.  Both PCOS and Hashimoto's thyroid disease cause infertility and both conditions are more likely to be found simultaneously in this group of patients.” 

Both physicians noted that patients presenting to clinics for reproductive evaluations are often screened already for both Hashimoto's thyroid disease and PCOS because of the known effects of these conditions on fertility. However, Dr. Angell told EndocrineWeb that “[t]hese findings build on our understanding of reproductive parameters in such patients,” but more research is required to confirm the outcomes reported in this study. 

Future Directions for Management of these Comorbid Conditions

“In summary, an increased prevalence of thyroiditis and hypothyroidism in PCOS appears to be established.  The presence of both PCOS and Hashimoto's disease appear to worsen the impact on metabolic, cardiovascular, and reproductive outcomes,” the authors wrote, but so far, no clear picture has emerged to explain the association by means of a common cause. 

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

Dr. Skugor proposed the following question, “Does treatment with thyroid hormones improve fertility in women with autoimmune (Hashimoto's) thyroiditis?” He recommended directing future studies to improve understanding of the impact of these conditions on pregnancy to better inform endocrinologists, given that previous studies have already indicated a critical role of thyroid hormone levels in managing fertility.

None of the authors had any financial disclosures to present.

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