Update in Endocrinology

Thyroid

Question: Does l-Thyroxine reduce the rate of miscarriage and premature delivery in euthyroid, pregnant women with thyroid autoantibodies who are treated early in their pregnancy?

Study Design: Randomized trial. Treating providers were not blinded to treatment assignment; patients and providers assessing outcomes were blinded.

Patients: 984 pregnant women (mean age, 29 years [SD, 5]), including 115 (11.7%) who were positive for thyroid peroxidase antibody (TPOAb). Women with overt hypo- or hyperthyroidism or preexisting thyroid dysfunction were excluded.

Setting: Brindisi, Italy.

Intervention:l-Thyroxine, 0.5 to 1.0 µg/kg per day, based on thyroid-stimulating hormone (TSH) level (57 TPOAb-positive women) or no treatment (58 TPOAb-positive women); 869 TPOAb-negative women were control participants.

Outcomes: The primary outcomes were obstetric complications, such as gestational hypertension, severe preeclampsia, and preterm birth before 37 weeks of gestation.

Follow-up: First visit to 3 days after delivery.

Results: The TPOAb-negative women were younger than the TPOAb-positive women (28 years [SD, 5] vs. 30 years [SD, 6]; P < 0.05). At baseline, TSH levels in TPOAb-positive women were higher than those in TPOAb-negative women, and they remained higher in untreated TPOAb-positive women than in treated TPOAb-positive and TPOAb-negative women. Untreated TPOAb-positive women had more miscarriages (13.8%) than did those treated with l-thyroxine (3.5%; relative risk, 1.72 [95% CI, 1.13 to 2.25]; P < 0.05) or those in the control group (2.4%; relative risk, 4.95 [CI, 2.59 to 9.48]; P < 0.01). The untreated TPOAb-positive group also had more premature deliveries (22.4%) than did the group that received l-thyroxine (7%; relative risk, 1.66 [CI, 1.18 to 2.34]; P < …