Endocrine Abstracts

TSH is involved in the immunomodulation of early pregnancy stages. Thyroid guidelines have indicated 2.5 mU/l as the best TSH level below which women undergoing assisted reproductive technology (ART) need to be maintained, though this treshold is still controversial. Aims of the present study were to evaluate if pre-conceptional TSH is associated with an increased risk of miscarriage, to identify a TSH cut-off significantly associated with risk of miscarriage and to assess the impact of TSH levels on primary and surrogate outcomes. A series of 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 was retrospectively studied. The majority of patients (60.8%) submitted to ART cycles had a primary infertility, while the remaining cases had a secondary infertility. 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. Embryo transfer was performed in 86% of cycles. A biochemical pregnancy was recorded in 369/1274 (29%) patients and 146 of them (39.5%) experienced a pregnancy loss. Moreover, among these 146 women, 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 observed between women with different times of miscarriage. ROC curve analysis showed that a TSH of 3 mU/l is significantly associated with miscarriage (P = 0.001), while a TSH of 2.3 mU/l is associated with a higher chance to have a biochemical pregnancy. These two TSH thresholds (2.3 or 3 mU/l) were also studied in relation to surrogate outcomes: we observed a weak association between TSH≤2.3 mU/l with the number of retrieved oocytes (P = 0.04) while no significant correlation was found with the number of either embryos obtained or transferred (P = NS). In conclusion, lower pre-conceptional TSH levels appears to favor the embryo implantation and to reduce the risk of early pregnancy loss in women undergoing ART. TSH screening prior to IVF procedures and L-T4 treatment are strongly recommended in order to optimize TSH levels before ovarian stimulation.