Resolved hyperthyroidism before IVF is not associated with improved cumulative live birth rates: a retrospective cohort study.

BACKGROUND

Hyperthyroidism adversely impacts female reproduction, yet its association with in vitro fertilization (IVF) outcomes remains controversial. It remains unknown whether ovarian function recovers upon achieving euthyroidism. We compared the IVF outcomes among women with active hyperthyroidism (AH), resolved hyperthyroidism (RH), and normal control (NC) patients.

METHODS

This retrospective study included patients undergoing their first oocyte retrieval cycle from January 2014 to September 2022, the follow-up lasted for two years. Thyroid function (TSH, FT3, FT4) was classified using the most recent test performed within 3 months before oocyte retrieval. Patients were categorized into three groups: AH, RH, and NC group based on the thyroid hormone level and disease history. The primary outcome was cumulative live birth rate (CLBR) per aspiration cycle. Multivariable logistic regression and inverse probability weighting (IPW) were used to evaluate the association, with adjustment for baseline characteristics and treatment protocols. Subgroup analysis examined the association between hyperthyroidism duration and CLBRs in patients in the AH/RH groups.

RESULTS

17,621 patients were involved, with 257 in the AH group, 297 in the RH group, and 17,067 in the NC group. The fresh cycle LBR was significantly lower in group AH compared to NC (31.9% vs. 43.7%, P = 0.034). CLBRs were 42.3% in group AH, 44.1% in RH, and 54.9% in NC. Adjusted models revealed lower LBR and CLBR in group AH versus NC, and no significant differences between group AH and RH. In the subgroup of patients with hyperthyroidism, longer duration of hyperthyroidism was negatively associated with cumulative live birth (aOR=0.9990 (0.9985-0.9995), P< 0.001).

CONCLUSIONS

Preconception hyperthyroidism was associated with poorer IVF outcomes, and longer disease duration was associated with a lower CLBR.