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

History and Admission Findings: We report on a 24-year-old male patient who presented with worsening of the general condition and abdominal pain.
Investigations: 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.
Diagnosis: In light of the typical laboratory findings, a non-seminomatous extragonadal germ cell tumor was diagnosed. Hyperthyroidism was most probably HCG induced.
Treatment and Course: Initially the patient was treated with thyreostatic drugs. After initiation of chemotherapy and a marked decrease in beta-hCG, thyreostatic therapy could be terminated.
Conclusions: 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.
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