Female infertility related to thyroid autoimmunity: the ovarian follicle hypothesis

The aim of this study was to verify whether anti-thyroid antibodies are present in the follicular milieu of euthyroid infertile women with thyroid autoimmunity undergoing in vitro fertilization (IVF) and whether IVF outcome is different in affected women with respect to negative controls. A secondary endpoint was to check whether there are changes in thyroid hormone levels during the IVF cycle.

Anti-thyroglobulin and anti-thyroperoxidase levels were measured in both follicular fluid and serum on the day of oocyte retrieval in women with thyroid autoimmunity. Serum TSH, FT3, and FT4 levels were measured in all patients before treatment initiation, on the day of oocyte retrieval and of pregnancy test. IVF outcome parameters were recorded in all women.

Oocyte fertilization, grade A embryos, and pregnancy rates were lower in women with thyroid autoimmunity than in negative controls, while early miscarriage rate was higher. Anti-thyroid antibodies were measurable in follicular fluid in all affected women and were strongly correlated with serum levels. No significant changes in thyroid hormone levels were recorded in any women.

The presence of anti-thyroid antibodies in ovarian follicles, as demonstrated for the first time in this study, may play a critical role in female infertility related to thyroid autoimmunity.