Investigating the optimal preconception TSH range for patients undergoing IVF when controlling for embryo quality

The ideal thyroid-stimulating hormone (TSH) range for infertile women attempting conception has not been determined. Current recommendations include optimizing the preconception TSH value to ≤2.5 mIU/L, which is the established goal for pregnant women. The aim of this study was to determine if there is a distinct range of TSH ≤2.5 mIU/L for infertile women undergoing in vitro fertilization (IVF) that improves reproductive outcomes.

One thousand five hundred ninety-nine euploid blastocyst transfer cycles were evaluated in which TSH measurements were obtained 8 days after embryo transfer. Only euploid embryo transfers were included in an effort to control for embryo quality. Patients were separated into TSH groups utilizing 0.5 mIU/L increments. Implantation, live birth, and miscarriage rates among the TSH groups were compared. Outcomes for individuals on thyroid hormone supplementation and those not requiring supplementation were evaluated.

There was no difference in implantation (p = 0.56), live birth (p = 0.36), or miscarriage rates (p = 0.10) between TSH groups. Receiver operating characteristic (ROC) curves for implantation, live birth, and miscarriage approached the line of no discrimination, signifying that there is no value of TSH within the recommended range for pregnancy (≤2.5 mIU/L) that predicts IVF outcomes better than other values in this range. Live birth rates for patients requiring thyroid hormone supplementation and those not on medication were similar (p = 0.86).

The recommended TSH range for pregnancy (≤2.5 mIU/L) may be applied to infertile patients attempting conception without a need for further adjustment.