Development of Graves' hyperthyroidism duringthe early phase of pregnancy in a patient with pre-existingand long-standing Hashimoto's hypothyroidism

摘要

Dear Sirs,it is well known that hypothyroidism may develop during the natural history of Graves' disease (GD), either as an effect of a shift of thyrotropin receptor antibodies (TRAb) from stimulating to blocking, or as consequence of an evolution of underlying immune process sustained by a shift from Th2 to Th1 immune response at thyroid gland level (1). Conversely, only few cases of Graves' hyperthyroidism following Hashimoto's hypothyroidism have been described as expression of a shift from blocking to stimulating TRAb (2-5). Moreover, in patients having circulating TRAb during pregnancy these antibodies may change their biological properties (6) as well as their concentrations (7), with a consequent turning of the clinical picture of autoimmune thyroid disease (ATD). Hence, hyperthyroid patients may either remit or become hypothyroid in pregnancy (8). On the other hand, hypothyroid TRAb+ patients may develop hyperthyroidism if these antibodies change their biological property from blocking to stimulating (5). Finally, it has been suggested that all hypothyroid women undergoing pregnancy need an empiric increase in Ievo-T4 (L-T4) dosage due to the known increase of thyroid hormone requirement (9). In consideration of this pathophysiological and therapeutical background, we think it is of some interest to briefly report a case, which we recently observed, of a woman with long-standing primary hypothyroidism due to Hashimoto's thyroiditis (HT) without TRAb, who developed TRAb+ Graves' hyperthyroidism during the first weeks of pregnancy.