Abortion may be associated with elevated risk of future hypothyroidism

OBJECTIVE: Fetal microchimerism during pregnancy and abortion has been linked with autoimmune hypothyroidism in females. We conducted a case–control study to investigate the odds of “abortion in the past” in the newly diagnosed hypothyroid females compared to their age-matched euthyroid controls. METHODS: All consecutive newly diagnosed hypothyroid females, over 1 year, were enrolled as cases. Age-matched euthyroid controls were selected from the same region. The exposure variable tested was “past history of abortion (elective or therapeutic).” RESULTS: Totally, 120 cases and 172 controls were recruited over 1 year with a mean age of 42.2 ± 9.8 years and 41.1 ± 12.4 years, respectively. The exposure variable (abortion) was present in 71 (59%) cases and 10 (6%) controls. Odds ratio (OR): 23.5 (12.2–48.9) P < 0.0001. Autoimmunity, based on thyroid peroxidase (TPO) positivity (TPO levels ≥30 U/ml), was present in 92 (77%) of the cases; TPO was negative in 28 (33%) of cases. The exposure variable was documented in 62.4% and 50% of TPO positive and negative cases, respectively (P = 0.28). DISCUSSION AND CONCLUSION: The study suggests that abortion (elective or therapeutic) in the past is strongly associated with newly diagnosed hypothyroidism in females aged 42.2 ± 9.8 years; OR: 23.5 (P < 0.0001). Interestingly, abortion was associated with both, TPO positive and negative hypothyroidism.