The impact of thyroid function and thyroid autoimmunity on embryo quality in women with low functional ovarian reserve: A case-control study

Background: Women with hyper-and hypothyroidism are at increased risk for infertility and adverse pregnancy outcomes. Whether in women considered euthyroid thyroid function (TSH values) and thyroid autoimmunity (thyroid antibodies) influence in vitro fertilization (IVF) cycle outcome has, however, remained controversial. Any such effect should be easily visible in women with low functional ovarian reserve (LFOR) and thus small oocyte and embryo numbers. Methods: We evaluated the relationship between TSH levels and embryo quality in euthyroid women with LFOR undergoing IVF. Mean age for the study population was 39.9 ± 4.6 years. Embryo quality was assessed in 431 embryos from 98 first IVF cycles according to TSH levels (with cut-off 2.5μIU/mL), and to presence versus absence of thyroid autoantibodies. Results: Mean Anti Mullerian hormone (AMH) was 0.8 ± 0.8 ng/mL and mean TSH was 1.8 ± 0.9 μIU/mL. Comparable embryo quality was observed in women with TSH ≤ and >2.5μIU/mL. TPO antibodies significantly affected embryo quality in women with low-normal TSH levels (P = 0.045). In women with high-normal TSH levels, increasing TSH had a negative impact on embryo quality (P = 0.027). A trend towards impaired embryo quality with TPO antibodies was also observed in these patients (p = 0.057). Conclusions: TPO antibodies affect embryo quality in euthyroid women with low-normal TSH ≤2.5 μIU/mL. In women with high-normal TSH levels, increasing TSH levels, and possibly TPO antibodies, appear to impair embryo quality. These results suggest that the negative impact of thyroid autoimmunity becomes apparent, once thyroid hormone function is optimized.