Diffuse metastasized testicular teratoma and paraneoplastic thyreotoxicosis. Case report and literature review.

Paraneoplastic syndromes are rare entities in patients with excessive HCG production. This has been attributed to the thyroid-stimulating hormone-like activity of HCG. In most cases hyperthyroidism remains subclinical. We report on a patient with diffuse metastasized malignant teratoma and thyrotoxicosis due to excessive levels of tumor-derived HCG. This complication of nonseminomatous germ cell tumors is associated with potential morbidity and the need for prompt recognition is stressed. Treatment consists of standard antithyroid medication and immediate cytoreductive chemotherapy to reduce the paraneoplastic stimulus. Evaluation of thyroid hormone levels in all patients with serum HCG levels exceeding 20,000 U/l is recommended.