Thyrotoxicosis due to the simultaneous occurrence of silent thyroiditis and Graves' disease

Silent thyroiditis (ST) and Graves' disease (GD) are two clinical entities belonging to the wide spectrum of autoimmune thyroid diseases (AITD). The two diseases are closely linked because sequential development of GD followed by ST, or the reverse course of events, ie, ST followed by GD, have been documented. However, the pathogenetic basis of the above association remains unknown. Some authors have suggested that the concomitant existence of ST and activation of GD can occur in thyrotoxic postpartum women with normal radioiodoine uptake. The simultaneous occurrence of the two diseases in different parts of the same thyroid gland has, however, to our knowledge, not been documented. We report the case of a 40-year-old thyrotoxic female with atypical presentation of GD. The titers of the antithyrotropin receptor antibodies were elevated and her initial 99mTc-pertechnetate thyroid scan showed the coexistence of ST and GD in different parts of the thyroid gland. Through serial thyroid scans, we document the recovery from ST in parts of the gland and demonstrate the progression to Graves' hyperthyroidism in the entire gland.