Background: Thyroid autoimmunity (TAI) is frequent in infertile women, but to what extent thyroglobulin autoantibodies (Tg-Abs) contribute to TAI is unclear in the literature. The aims of the present study were to determine the prevalence of TAI in women consulting for fertility problems and to investigate the impact of isolated Tg-Abs, isolated thyroid peroxidase autoantibodies (TPO-Abs), and the presence of both autoantibody types on thyroid function. Furthermore, thyroid function was compared between women with and without TAI and between infertile and fertile women.
Methods: A cross-sectional data analysis nested within an ongoing prospective cohort study was performed in order to determine the prevalence of TAI in unselected women consulting our tertiary referral center for reproductive medicine (CRM). The women underwent a determination of serum thyrotropin (TSH), free thyroxine (FT4), TPO-Abs, and Tg-Abs. The cause of infertility, age, body-mass index (BMI), and smoking habits were recorded.
Results: The prevalence of TAI was 16% (163/992). In 8% of cases, both types of autoantibodies were present, in 5% isolated positive Tg-Abs were found, and 4% had isolated positive TPO-Abs (p=0.025 and p=0.003 respectively). The prevalence of TAI was significantly higher in infertile women as compared to that in fertile controls (19% vs. 13%; p=0.047). The median serum TSH level was significantly higher in the women with TAI and with isolated positive Tg-Abs compared to that in women without TAI (1.83 [1.44] and 1.90 [0.85] vs. 1.47 [0.94] mIU/L; p<0.001 respectively). The median FT4, age, BMI, and smoking habits were comparable between the study groups.
Conclusions: The prevalence of TAI was higher in infertile women as compared to fertile women consulting our CRM. Five percent of the women had isolated positive Tg-Abs and a significantly higher serum TSH compared to that in women without TAI.