Endocrine Abstracts

Aim: To evaluate the usefulness of measuring maternal anti-TSH receptor antibodies (TRAbs) and fetal ultrasound (US) monitoring in cases of current or past maternal hyperthyroidism.

Materials and methods: A 77 pregnant women with active hyperthyroidism irrespective of its cause or with history of Graves’ hyperthyroidism were observed prospectively. Maternal serum TSH, fT₄, fT₃, TRAbs, and fetal US were performed at baseline and repeated every 2–4 weeks when needed. Neonatal thyroid status was assessed based on serum TSH, fT₄, and fT₃ obtained in the first days of life.

Results: A 35 women were diagnosed with gestational hyperthyroidism and 42 with Graves’ disease; among them 26 had current and 16 past hyperthyroidism. Fetal and neonatal thyroid dysfunction occurred only in cases of maternal Graves’ disease: 9 (21%) and 3 (7%) respectively. Active maternal Graves’ hyperthyroidism and TRAbs elevated at least five times above the upper normal limit predisposed to fetal hyperthyroidism. Maternal anti-thyroid drug therapy, and low TRAbs and fT₄ were the risk factors of fetal hypothyroidism. Abnormal fetal thyroid sonogram was the only indication of fetal thyroid dysfunction. Increased blood flow throughout the whole thyroid gland (central hypervascularization), hypoechogenicity, goiter or thyroid size in the upper normal range were fetal signs characteristic for hyperthyroidism. Goiter without increased vascularization or with increased peripheral blood flow represented fetal sign of hypothyroidism. Four patients had high TRAbs in the third trimester (10.8–29.9 IU/ml), but neither fetal nor neonatal thyroid dysfunctions were noted.

Conclusions: In the cases of maternal Graves’ disease, fetal thyroid dysfunction occurs more often than commonly assumed. Fetal thyroid US is a valuable tool in early diagnosing and monitoring of the fetal thyroid status in pregnancy complicated by maternal Graves’ disease. The evaluation of biological activity of maternal TRAbs may be helpful in prenatal diagnosis in some cases.