AUTHOR=Palomba Stefano , Colombo Carla , Busnelli Andrea , Caserta Donatella , Vitale Giovanni TITLE=Polycystic ovary syndrome and thyroid disorder: a comprehensive narrative review of the literature JOURNAL=Frontiers in Endocrinology VOLUME=Volume 14 - 2023 YEAR=2023 URL=https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2023.1251866 DOI=10.3389/fendo.2023.1251866 ISSN=1664-2392 ABSTRACT=Background: Published data on the relationship between polycystic ovary syndrome (PCOS) and thyroid dysfunction are sparse and confusing. Objective: To comprehensively review data available in the literature regarding the relationship between PCOS and the thyroid function, and its abnormalities. Methods:An extensive literature search for specific keywords was performed for articles published from 1970 to March 2023 using PubMed and Web of Science. Nine main areas of interest were identified and analyzed according to the available evidence. Data were reported in a narrative fashion. Results: PCOS is a diagnosis of exclusion for which diagnosis is possible only after excluding disorders that mimic the PCOS phenotype, including thyroid dysfunctions. However, the tests and the cutoff values used for this are not specified. Many experimental and clinical data suggest a relationship between perturbations of the thyroid function and PCOS. Direct and unequivocal evidence on the effects of thyroid function/disorders on PCOS features are lacking. High thyroid-stimulating hormone levels and subclinical hypothyroidism may be associated with significant worsening of several intermediate endpoints of cardiometabolic risk in women with PCOS. Thyroid abnormalities may worsen reproductive outcomes, especially in patients undergoing fertility treatment. To date, there are no data demonstrating the efficacy of thyroid medications on fertility and cardiometabolic risk in women with PCOS. Lifestyle modification changes, metformin, and vitamin D seem to improve thyroid function in the general population. Conclusion: PCOS and thyroid disorders are closely related, and their coexistence may identify patients with a higher reproductive and metabolic risk. Regular screening for thyroid function and thyroid-specific autoantibodies in women with PCOS, particularly before and during pregnancy, is highly recommended.