Relationship between thyroid disorders and uterine fibroids among reproductive-age women

Uterine fibroids and thyroid nodules, both of which are crucially affected by estrogen, are common diseases among reproductive-age women. However, little attention has been paid to the association between the two diseases. This retrospective case-control study aimed to assess the relationships among thyroid nodules, thyroid function and uterine fibroids in China. We reviewed the electronic records of 853 reproductive-age women who attended health check-ups at the Second Affiliated Hospital of Wenzhou Medical University from July 1st, 2017, to June 30th, 2018. All subjects received transvaginal pelvic ultrasound, thyroid ultrasound, thyroid function, and other laboratory tests. We found that the prevalence of thyroid nodules in subjects with uterine fibroids was remarkably higher than that in subjects without fibroids. The proportion of thyroid nodules ≥1 cm in subjects with uterine fibroids was significantly higher than that in subjects without fibroids. Women with thyroid nodules had a higher proportion of multiple uterine fibroids than women without thyroid nodules. Among the parameters of thyroid function, the only statistically significant parameter was total triiodothyronine, i.e., women with uterine fibroids had lower total triiodothyronine levels than unaffected controls; however, the total triiodothyronine levels were within the normal ranges. Moreover, no significant difference was noted in thyroid hormone status between subjects with and without uterine fibroids. Our findings suggest that thyroid nodules are positively correlated with uterine fibroids among reproductive-age women in China. Further studies are needed to confirm this association and fully understand the common pathogenetic mechanism underlying the association between uterine fibroids and thyroid nodules.