Thyroid Peroxidase Autoantibodies Predict Poor Metabolic Control and Need for Thyroid Treatment in Pregnant IDDM Women

OBJECTIVE To study whether the presence of antithyroid peroxidase antibodies (TPO-Abs) before gestation in IDDM affects thyroid function and metabolic control during pregnancy and early postpartum as well as neonatal outcome. RESEARCH DESIGN AND METHODS A prospective study at an outpatient endocrine-obstetric unit was carried out in 20 pregnant IDDM women. Free T4 (thyroxine), thyroid-stimulating hormone (TSH), TPO-Abs, and HbA 1c were assayed before gestation; during the first, second, and third trimester of pregnancy; and 3 months postpartum. RESULTS HbA 1c was significantly higher in TPO-Ab+ women than in those who were TPO-Ab − during the second ( P P 1c levels significantly decreased in TPO-Ab − patients when the second ( P P − patients during the second ( P P P P P P − patients; 7.6% of the TPO-Ab − group and 29% in the TPO-Ab+ group presented postpartum thyroid dysfunction, and 42% of the TPO-Ab+ women required thyroid treatment. CONCLUSIONS Pregnant women with IDDM who have a positive test for TPO-Abs before gestation have poorer glucose control and a high prevalence of hypothyroidism. Therefore we recommend that prepregnant IDDM patients be screened for anti-TPO-Abs. Those with a positive result should be followed with serial monitoring of free T4 and TSH levels during each trimester as well as the postpartum period.