What is the impact of thyroid cancer history on in vitro fertilization: A cohort study

Background: The incidence of thyroid cancer is increasing every year. Surgical resection is one of the main treatments for thyroid cancer, but it can affect thyroid function. In women of childbearing age, thyroid dysfunction is associated with infertility. The aim of this study was to investigate the changes in fertility and the risk of adverse outcomes in women with thyroid cancer (post-thyroidectomy) combined with infertility. Methods This retrospective cohort study included 17086 in vitro fertilization (IVF) cycles from January 2014 to March 2022 at the Sun Yat-Sen Memorial Hospital Reproductive Center, Sun Yat-Sen University. A 1:4 propensity score matching was used to match the thyroid cancer group with the control group. Categorical variables were tested with chi-square test and continuous variables with Kruskal test to analyze the differences in baseline characteristics, thyroid stimulating hormone (TSH), number of mature follicles, number of eggs gained, normal fertilization rate, quality embryo rate and pregnancy outcome between the two groups. Generalized estimating equation was used to investigate the effects of TSH on clinical pregnancy and live birth in the two groups. Results The thyroid cancer group had significantly lower TSH levels than the control group (median: 1.27 mIU/L vs. 1.58 mIU/L, P  = 0.017). However, the number of retrieved oocytes, normal fertilization rate, good quality embryo rate, clinical pregnancy rate, and live birth rate were not significantly different between the two groups ( P  > 0.05). History of thyroid cancer and TSH have an interactive effect on live birth rate (RR: 2.280, 95%CI: 1.126, 4.616, P  = 0.022), but not clinical pregnancy rate ( P  < 0.05). Conclusions Our study showed that IVF-ET outcomes in infertile women were not affected by the history of thyroid cancer (post-thyroidectomy), but the live birth rates were more affected by TSH level. The thyroid function of patients with a history of thyroid cancer should be checked regularly and remained at a normal range. Trial registration This study was approved by the Ethics Committee of Sun Yat-sen Memorial Hospital, Sun Yat-sen University (SYSKY-2022-082-01)