Endocrine Abstracts

Women with positive thyroid autoimmunity are considered at risk of developing hypothyroidism in pregnancy, so monitoring thyroid function is recommended.

Objective: To assess the risk of gestational hypothyroidism in pregnant women with autoimmune thyroid disease and normal thyrotropin (TSH) at the beginning of pregnancy.

Methods: Retrospective review of data from pregnant women attended between April 2016 and October 2019. Women with positive anti peroxidase (anti-TPO) and/or anti thyroglobulin (anti-Tg) antibodies, and normal TSH level in the first trimester (TSH 0.1–4.0 mIU/l) were selected. Thyroid function was monitored throughout pregnancy to assess the development of gestational hypothyroidism, defined as TSH ≥4 mIU/l.

Results: Ninety-nine pregnant women were included, aged 34.2 ± 4.7 years (18–43), 40.4% nulliparous, with mean baseline TSH 1.91 ± 1.05 mIU/l (9th gestational week).

Anti-TPO antibodies were positive in 86.9% of women. All anti-TPO negative women were positive for anti-Tg antibodies. Twelve women were lost during follow-up.

Only 2 women developed hypothyroidism (2%). These women had baseline TSH levels > 2.5 mIU/l and reached TSH 4.01 and 4.23 mIU/l respectively in the 15th gestational week, starting treatment with levothyroxine.

Conclusion: In our population, women with positive thyroid autoimmunity and normal TSH levels in the 9th week, appears to have very low risk of developing gestational hypothyroidism. These women would need no additional follow-up during pregnancy.