Thyroid autoimmunity turns up far more often in women with PCOS

Polycystic ovary syndrome and Hashimoto thyroiditis are both common endocrine disorders in women, and when they occur together the concern is that each makes the other's consequences worse. Despite how common both conditions are, the literature examining their overlap has been scarce and scattered across small individual studies. This meta-analysis set out to establish two things: how much more common Hashimoto thyroiditis actually is among women with PCOS, and whether carrying both conditions worsens insulin resistance and blood lipids compared with PCOS alone.

The authors systematically searched PubMed, Embase, Web of Science and Google Scholar from inception to February 2026, using terms covering polycystic ovary syndrome, Hashimoto thyroiditis, autoimmune thyroid disease, insulin resistance and metabolic outcomes. The search retrieved 209 articles, of which 38 full texts were screened and 22 studies were included in the final meta-analysis. The pooled comparisons covered the prevalence of Hashimoto thyroiditis in women with PCOS versus controls, plus insulin resistance and lipid profiles in women with PCOS with and without the thyroid condition.

Hashimoto thyroiditis was substantially more prevalent among women with PCOS, with 2.69 times the odds compared with control subjects. Women who had both PCOS and Hashimoto thyroiditis showed significantly higher insulin resistance, measured by HOMA-IR, than women with PCOS alone. The lipid picture, however, was flat: total cholesterol, LDL, HDL and triglycerides were all statistically similar between women with PCOS regardless of whether they also had the thyroid condition.

This pooled analysis firms up what individual studies had hinted: the two conditions cluster together well beyond chance, and the combination carries a measurable metabolic cost in the form of worse insulin resistance. Because the underlying studies compared existing groups of women rather than testing anything, the analysis cannot untangle which condition drives which, or whether a shared cause underlies both. The authors call for prospective studies with long follow-up to answer those questions.

For women living with PCOS, this is knowledge worth having rather than a call to action: thyroid autoimmunity travels alongside the condition often enough that the link is worth being aware of, particularly since the combination was tied to higher insulin resistance. The reassuring part is that blood fats did not look worse in women carrying both conditions. Nothing here establishes cause, and what any individual should do about it remains a conversation for her own clinician.