It is well known that the clinical features of Graves' hyperthyroidism (GH) tend to improve during pregnancy, and smaller doses of antithyroid medication are needed to maintain euthyroidism [1], in parallel with fall in serum titres of thyroid peroxidase (TPO), thyroglobulin (Tg), and TSH receptor (TSHr) antibodies; the antibodies rebound in the postpartum period, at which time the hyperthyroidism often relapses [2]. This evidence concerns the gene TPO and hyperthyroidism.