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

Purpose: We retrospectively analyzed how the presence of thyroid autoimmunity (TAI positive) affected reproductive parameters in eighty-six (86) TAI positive women referred to IVF treatment. Methods: All participants diagnosed with subclinical or overt hypothyroidism, while euthyroid on thyroxine replacement. Sixty-nine (69) female patients in the same IVF program, with no thyroid abnormalities served as controls (TAI negative group). Results: Statistically significant baseline hormone profile differences were found in multiple parameters between the two groups. TAI positive women were older (mean age 34.7±5.42 vs. 32.32±5.04 years; p=0.002), had higher FSH (8.4±3.49 U/L vs. 7.04±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 their AMH (2.88±2.62 vs. 3.6±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 (1.304±0.29 vs. 1.13±0.21 ng/dl; p=0.0002) was higher in the TAI positive group. Egg cell counts (6.0±3.82 vs. 7.5±3.95; p=0.015), clinical pregnancy rate (36.04 % vs. 69.56 %; p<0.001), live birth rate (23.25 % vs. 60.86 %) were lower, the miscarriage rate (35.48 % vs. 12.5 %; p=0.024) was higher in the TAI positive group. There was no difference in ICSI fertilization rate (69.12 % vs 62.91 %, p=0,12), although the fertilization rate was lower for patients under 35 in the TAI positive group, after adjusting for age. Conclusion: TAI positive women carry a multitude of endocrine and metabolic parameters which may contribute to unfavorable effects on reproductive health.