Thyroid Research Thyroid Research Archive Graves' Disease

Only mothers with severe Graves' disease give birth to infants with hyperthyroidism

(November 2002)

The background of the study. Fetuses and neonates of mothers who have Graves' disease may have hyperthyroidism, caused by the transplacental passage of thyrotropin (TSH)-receptor-stimulating antibodies. This study was done to determine the relationship between maternal serum concentrations of these antibodies and the risk of fetal or neonatal hyperthyroidism.

How the study was done. Serum TSH-receptor-stimulating antibodies were measured during the second trimester of pregnancy in 61 women with a history of Graves' disease. Among the 49 women who had positive tests for the antibodies, prenatal and delivery records were available for review in 29 (59 percent). Neonatal hyperthyroidism was defined as symptoms and signs of hyperthyroidism (tachycardia, goiter, irritability, hyperphagia, heart failure) and high serum free thyroxine and low serum TSH concentrations.

The results of the study. The 29 women (mean age, 29 years) had 35 singleton pregnancies ending with live births. During these pregnancies, 11 women were treated with propylthiouracil, 8 with thyroxine for hypothyroidism caused by radioiodine treatment or surgery, 6 with propylthiouracil and thyroxine, and the remainder with neither treatment. Among the 35 infants, 6 (17 percent) had neonatal hyperthyroidism, including two infants delivered by each of two mothers. Five of these 6 infants had tachycardia and 2 had heart failure; all were treated with propylthiouracil. Among the mothers of these 6 infants, all (100 percent) had serum TSH receptor-stimulating antibody values more than five times the upper limit of normal. Among the 29 normal infants, the mothers of only 6 (21 percent) had serum values more than five times the upper limit of normal.

The conclusions of the study. Among pregnant women with Graves' disease, only the infants of those with very high serum thyroid-stimulating immunoglobulin index values are at risk for hyperthyroidism.

The original article. Peleg D, Cada S, Peleg A, Ben-Ami M. The relationship between maternal serum thyroid-stimulating immunoglobulin and fetal and neonatal thyrotoxicosis. Obstet Gynecol 2002;99:1040-3.