[Hyperthyroidism as a diagnostic key to advanced choriocarcinoma. An unusual association].

Hyperthyroidism is a relatively frequent condition with multiple causes. The most common cause is Graves' disease; followed by hyperthyroid multinodular goiter and toxic adenoma. Association between hyperthyroidism and cancer is infrequent in daily practice. We present the case of a 42-year-old man who developed severe symptoms of hyperthyroidism within a period of two months. Physical examination revealed significant hepatomegaly. Testicular examination proved normal. Imaging studies showed the presence of multiple hepatic solid lesions consistent with metastases. After discarding the most common causes of hyperthyroidism and primary thyroid gland neoplasm, the possibility of molecular mimicry was considered through human chorionic gonadotrophin production. Critical high values of this hormone were found and choriocarcinoma histological diagnosis was confirmed through a liver biopsy. We consider that the recognition of this rare mechanism of hyperthyroidism may be a clue permitting a faster diagnosis, particularly when extragonadal tumors are present.