Endocrine Abstracts

Background: thyroid function (TSH levels) and thyroid autoimmunity are involved in the immunomodulation of early pregnancy stages and can affect assisted reproductive technology (ART).

Aims: 1) to evaluate if pre-conceptional TSH is associated with an increased risk of miscarriage, 2) to identify a TSH cut-off significantly associated with risk of miscarriage, 3) to assess the impact of TSH levels on primary and surrogate outcomes.

Methods: We retrospectively studied 1484 infertile women (mean± age 36.7±4.1 years, mean± SD BMI 22.7±4) submitted to IVF in a single center from 2004 and 2014. 60,8% and 39.2% of cycles were performed in women affected with primary and secondary infertility, respectively. Primary outcomes were biochemical pregnancy, clinical pregnancy, miscarriage and delivery. Surrogate outcomes were the number of oocytes, the number of embryos and the transfer of embryos.

Results: In 86% of cycles an embryo transfer was performed. 369/1274 (29%) of patients had a biochemical pregnancy and 146 of them experienced a pregnancy loss. Moreover, among the 146 women with pregnancy loss, 52 (36%) were clinically pregnant and had a miscarriage in the first trimester, while in 94 patients (64%) a biochemical pregnancy without clinical evolution was documented. No significant differences in mean TSH levels were recorded between women with different time of miscarriage. By a ROC curve analysis we found that a TSH of 3 mU/l was significantly associated with miscarriage (P=0.001), while a TSH of 2.3 mU/l was associated with a higher chance to have a biochemical pregnancy. We further studied the relationship between the two TSH thresholds (2.5 or 3 mU/l) with surrogate outcomes and we observed a weak association between TSH <=2.5 mU/l with the number of retrieved oocytes (P=0.04) while no significant correlation was found with the number of embryos either obtained or transferred (P=NS).

Conclusion: In women undergoing IVF, lower pre-conceptional TSH levels seems to favor the embryo implantation and reduce the risk of early pregnancy loss. These data strongly indicate the need for TSH screening prior to IVF procedures and suggest LT4 treatment in order to optimize TSH before ovarian stimulation.