Improvement of idiopathic thrombocytopenic purpura by antithyroid therapy

Here we report a case of idiopathic thrombocytopenic purpura accompanied by Graves' disease. Improvement in thyroid function with methimazole led to the spontaneous recovery of the platelet count from 8 x 10(9)/L to 84 x 10(9)/L. Furthermore, the second fall and recovery of the platelet count well coincided with the recurrence of hyperthyroidism after the discontinuation of methimazole and its normalization by resumption of the drug, respectively. These parallel fluctuations of platelet and thyrotropin because of the cessation and resumption of antithyroid therapy suggests that correction of hyperthyroidism may be beneficial to the control of an imbalance in the immune system which impairs not only thyroid but also the platelet.