Prediction of neonatal hyperthyroidism in infants born to mothers with Graves disease.

OBJECTIVE

To determine whether determinations of thyrotropin-receptor antibody (TRAb) levels in newborn infants of women with Graves disease would predict which infants will have hyperthyroidism.

METHODS

The TRAb levels, assayed in the sera of 14 infants born to 14 women with Graves disease, were measured sequentially in the infants with hyperthyroidism during the course of antithyroid medication therapy.

RESULTS

Seven infants had TRAb values less than 0.15 and remained euthyroid. In seven infants whose initial TRAb values were more than 0.25 (range, 0.48 to 0.88), clinical and biochemical signs of hyperthyroidism developed. The infants were treated with antithyroid medication until day 57 to day 123 of life. Therapy was discontinued when the infants were free of symptoms and when serum thyroxine and triiodothyronine and free thyroxine levels remained normal during therapy with decreasing doses of antithyroid medication. When the medication was discontinued, TRAb values were less than 0.20.

CONCLUSIONS

Infants born to mothers with Graves disease with initial TRAb values less than 0.15 remained euthyroid. The TRAb values greater than 0.25 were associated with the development of neonatal hyperthyroidism. During treatment of neonatal hyperthyroidism, TRAb values less than 0.20 may be helpful in deciding when to withdraw antithyroid medication.