No Decrease in Pregnancy Rates After Radioactive Iodine Therapy

According to results from a systematic review and meta-analysis, most studies did not observe a decrease in pregnancy rates following radioactive iodine (RAI) therapy. These findings were published in Thyroid.

Researchers in the Netherlands queried publication databases through January 2020 for studies of women undergoing treatment for differentiated thyroid carcinoma during their reproductive years. A total of 22 studies were included in this analysis including 36,215 patients.

A total of 4 studies focused on the gonadal effects of RAI and 7 studies assessed RAI effect on the ovarian reserve. Women and girls received RAI between 8 and 45 years of age with cumulative doses from 2997 MBq to 59 GBq.

One study found during the first year following the RAI therapy, 12% of women reported a change to their menstrual cycle including amenorrhea that persisted between 4 and 10 months among 8% of patients. Another study reported more menstrual cycle alterations during the year following RAI therapy compared with an aged-match control cohort (31.1% vs 14.5%; P =.002).

Among premenopausal women who received RAI ablation for well-differentiated thyroid cancer, 15.6% had transient oligo/anovulation following their treatment.

At 1 year, 82% of women had anti-Mullerian hormone (AMH) levels below baseline levels (3.25 vs 2.36±1.88 ng/mL; P <.005). Higher doses of RAI were associated with decreased AMH, in which women receiving multiple RAI procedures had 85% reduction of AMH 4 years following their procedures compared with baseline (3.34±1.20 vs 0.95±1.23 ng/mL; P <.05).

Women who received suppressive levothyroxine in addition to the RAI entered menopause at a younger age (49.5 years) compared with women not receiving RAI (51 years; P <.001).

Among the studies that incorporated data on subsequent pregnancies, 2 observed an increase of spontaneous and induced abortions the year following RAI (26.19% vs 16.83%). However, the discrepancy was due more to induced rather than spontaneous abortion, and spontaneous abortions were decreased following RAI (10.3% vs 16.8%).

Studies reporting birth rates had conflicting results: 1 study reported decreased pregnancies following RAI (adjusted hazard ratio [HR], 0.77; 95% CI, 0.70-0.86; P <.001). Two other studies found a nonsignificant increase of pregnancies among patients treated with RAI (30.0% vs 29.3%) and the other, no difference between pregnancies compared with the general population (odds ratio [OR], 0.98; 95% CI, 0.72-1.33; P =.909).

This study was limited by the different methods for quantifying AMH among the various studies, making pooled analyses of results infeasible.

These data indicated there was no clear evidence to suggest RAI decreased pregnancy rates among women. There was sufficient evidence to suggest that AMH levels were lowered by RAI therapy, and further studies are needed to determine what effect decreased AMH has on fertility.

Reference

Piek MW, Postma EL, van Leeuwaarde R, et al. The effect of radioactive iodine therapy on ovarian function and fertility in female thyroid cancer patients: a systematic review and meta-analysis. Thyroid. Published online November 2, 2020. doi:10.1089/thy.2020.0356