Hashimoto’s thyroiditis negatively influences ICSI outcome in euthyroid women on T4 substitution therapy; a retrospective study

Objective: To analyze the impact of thyroid autoimmunity (TAI) on reproductive outcome parameters of ICSI cycles as compared to TAI negative ICSI cycles. Design: In this single IVF center retrospective study 86 infertile women with elevated TPOAb or TGAb levels, but euthyroid after thyroxine replacement (study group), were compared to 69 female patients with no thyroid abnormalities (controls). Following ICSI treatment fertilization rate (FR), clinical pregnancy rate (CPR), miscarriage rate (MR) and live birth rate (LBR) were analyzed. Materials, setting, methods: All subjects with various infertility factors were treated with ICSI in university based IVF center. Patients in the study group received thryroxine replacement and were euthyreoid at IVF treatment. Before the IVF cycles endocrinological parameters were uniformly assessed: thyroid function and antibodies, reproductive hormones (AMH, FSH, LH, E2, PRL, testosterone, DHEAS, 17-OHP, AD) and OGTT (0-60-120 min glucose and insulin). Following descriptive comparison of laboratory parameters, age adjusted analyses of FR, CPR, MR and LBR were performed. Results: TAI positive women were older (mean age 35.31±4.95 vs. 32.15±4.87 years; p=0.002), had higher FSH (8.4±3.4 vs. 7.4±2.32 U/L; p=0.024), higher E2 (53.94±47.61 vs. 42.93±18.92 pg/ml; p=0.025) levels, while AMH (2.88±2.62 vs. 3.61±1.69 ng/ml; p=0.0002) was lower. There were no differences in TSH levels (1.64±0.96 vs. 1.66±0.65 uIU/ml; p=0.652) between the two groups. FT3 (2.63±0.58 vs. 2.98±0.55 pg/ml; p=0.002) was lower and FT4 (1.3±0.29 vs. 1.13±0.21 ng/dl; p=0.0002) was higher in the TAI positive group, reflecting clinically irrevelant differences. Egg cell counts (6±3.8 vs. 7.5±3.95; p=0.015) were lower in TAI and remained so following age adjustment. Although the overall ICSI FR did not differ (62.9 % vs. 69.1 %, p=0.12), it was lower for patients under 35 with TAI showing decreasing differences in line with age. The CPR (36.04 % vs. 69.56 %; p<0.001), LBR (23.25 % vs. 60.86 %; p<0.001) were lower, the MR (35.48 % vs. 12.5 %; p=0.024) was higher in the TAI group and these differences remained after age adjustment. Limitations: Since the higher age of the study group may interfere with the effect of TAI, age adjustment calculations were necessary to perform to eliminate this confounding factor. Conclusion: Despite optimal thyroid supplementation in clinical or subclinical hypothyreoidism, the presence of TAI negatively influences clinical pregnancy rate and is connected to a higher miscarriage rate, thus resulting in a lower live birth rate after ICSI. Decreased fertilization rate with ICSI in TAI patients may also contribute to poorer outcomes, especially in younger women.