The Long-Term Impact Of Controlled Ovarian Hyperstimulation On Thyroid Function

Abstract

Evidence on the long-term impact of controlled ovarian hyperstimulation (COH) on thyroid function is scarce. To investigate this, we report on serum thyroid-stimulating hormone (TSH) modifications in euthyroid and hypothyroid women during COH and 3 months after the end of the stimulation cycle. Women who underwent in vitro fertilization (IVF) and who did not become pregnant were eligible. Cases were women with treated hypothyroidism and basal serum TSH <2.5 mIU/L. Controls were euthyroid women matched to cases by age and basal serum TSH. Women could be included if serum TSH was available at 4 time points: prior to initiating COH (time 1); at the time of human chorionic gonadotropin (hCG) administration (time 2); 16 days after hCG administration (time 3); and 3 months after the end of the IVF cycle (time 4). Thirty-seven case-control pairs were included. Serum TSH at times 1, 2, 3, and 4 was 1.7 ± 0.6, 3.1 ± 1.4, 3.1 ± 1.3, and 2.7 ± 1.7 mIU/L, and 1.7 ± 0.6, 2.9 ± 1.0, 2.7 ± 1.0, and 1.9 ± 0.7 mIU/L among cases and controls, respectively. A statistically significant difference emerged at time 4 (P<.001). In both groups, serum TSH was higher at time 4 compared to time 1. Serum TSH exceeded the recommended threshold of 2.5 mIU/L at time 4 in 51% of cases (95% confidence interval [CI], 35 to 68%) and in 16% of controls (95% CI, 4 to 28%) (P = .003). COH seems to have a long-term impact on TSH levels. The magnitude of this effect is particularly pronounced in hypothyroid women.