Endocrine Abstracts

Introduction: The evidence of the impact of OS for IVF and thyroid function or autoimmunity is inconclusive, based mainly on assessments just before and after OS. The aim of this study was to closely monitor the changes on thyroid function and autoimmunity throughout OS for IVF.

Description of methods/designs: In a prospective, interventional study, a flexible GnRH-antagonist protocol was applied to 42 women undergoing IVF ((classic or ICSI), with initiation according to follicular size and estradiol (E₂) concentrations. All women were assessed five times during OS (day 3 of menstrual cycle, day 5 of menstrual cycle, day of hCG administration, oocyte pick-up (OPU) day and day of pregnancy test (15 days after OPU)). Assessment included thyroid function tests (TSH, fT₃, and fT₄) and autoimmunity (anti-TPO, and anti–Tg).

Results: Women had a median (inter-quartile range) age of 36 (6) years, BMI 22.6 (4.8) kg/m² and baseline mean (±S.E.M.) TSH 1.82±1.55 μIU/ml, fT₃ 3.37±0.05 pmol/l and fT₄ 1.30±0.03 ng/dl. A significant increase was recorded in TSH concentrations between OPU day and the day of the pregnancy test (P=0.017), whereas anti-TPO concentrations were decreased (P=0.043). No changes were recorded in fT₃ and fT₄ concentrations throughout OS.

Conclusion: This study demonstrated that OS can influence thyroid function and this influence is reflected in TSH concentrations, 15 days after OPU. As the threshold for TSH concentrations for the first trimester of pregnancy is particularly low (<2.5 μIU/ml), special care, such as universal baseline screening and levo-thyroxine supplementation in selected cases, have to be considered in women undergoing OS for IVF.