The influence of selenium supplementation on postpartum thyroid status in pregnant women with thyroid peroxidase autoantibodies.

Randomized placebo-controlled study in euthyroid pregnant women who were positive for thyroid peroxidase antibodies. The selenium arm (Group S1) had 85 women randomized, with 77 analyzed; all participants were Caucasian women in Italy.

Selenomethionine 200 microg daily, started no earlier than 12 weeks' gestation and continued through pregnancy and the postpartum period, compared with placebo. Route of administration was not stated.

Selenium supplementation lowered postpartum thyroid dysfunction and permanent hypothyroidism compared with placebo. Within 12 months after delivery, thyroid dysfunction occurred in 28.6% of the selenium group versus 48.6% of the placebo group, and permanent hypothyroidism occurred in 11.7% versus 20.3% (both P < 0.01). Selenium also produced a larger fall in TPOAb during gestation, 62.4% versus 43.9% (P < 0.01), and lower postpartum TPOAb titers, including the peak around 5 months postpartum: 383.4 Ϯ 148 kIU/liter versus 745.5 Ϯ 257 kIU/liter (P < 0.01). Thyroid ultrasound patterns improved more in the selenium group by the end of the postpartum period, and no adverse effects from excess selenium intake were observed.

The selenium arm was relatively small, with 85 randomized and 77 analyzed, and the cohort was limited to Caucasian women in Italy, which may reduce generalizability. Route of administration was not stated, and the long-term durability of benefit after selenium discontinuation was not established.