Table 1. Exclusion criteria.

Known thyroid disease, current or previous treatment with antithyroid drugs or L-T4
History of 131I therapy, thyroidectomy or head and neck external radiotherapy
Age > 30 years
Type 1 diabetes or other autoimmune diseases
History of pregnancy loss, preterm delivery, or infertility
Multiple prior pregnancies (≥ 2)
Family history of autoimmune thyroid disease or thyroid dysfunction
Morbid obesity (BMI ≥ 40 kg/m2)
Use of amiodarone, interferon, or lithium; or recent (in the past 8 weeks) exposure to iodinated contrast agents
Goiter, palpable thyroid anomaly or ophthalmopathy