[Endocrine abnormalities in a young patient with metastatic cancer - case 3/2013].

We report on a 24-year-old male patient who presented with worsening of the general condition and abdominal pain. On physical examination, gynecomastia was noted. Laboratory tests showed manifest hyperthyroidism. The beta-hCG levels were markedly increased. By ultrasound, the thyroid gland was hyperperfused without thyroid nodules. Several large echo mixed lesions were found in the liver. The testes appeared normal. In light of the typical laboratory findings, a non-seminomatous extragonadal germ cell tumor was diagnosed. Hyperthyroidism was most probably HCG induced. Initially the patient was treated with thyreostatic drugs. After initiation of chemotherapy and a marked decrease in beta-hCG, thyreostatic therapy could be terminated. Germ cell tumors may cause an increase in beta-hCG concentration. By cross-reacting with the TSH-receptor this could induce hyperthyroidism. Germ cell tumors are therefore a rare differential diagnosis of hyperthyreoidism.