We describe the case of a 24 year old man with metastatic non-seminomatous germ cell tumour who presented with hyperthyroidism and gynaecomastia associated with elevated human chorionic gonadotrophin(HCG). Following a 3 month history of gynaecomastia, flank pain, nausea and 7kg weight loss, the patient attended the emergency department with persistent vomiting. Initial laboratory investigations reported TSH <0.05mU/L (normal range 0.3-4.3) and free T4 29.5pmol/L (12-22), TPO antibodies

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... ve, FSH <1 and LH 1 U/l, testosterone >52 nmol/L (9-29.0), bioactive prolactin 1048mU/L (63-245), SHBG 110.6 nmol/l (18.3-54.1), and oestradiol 3935pmol/L (<223). Clinical examination revealed bilateral tender gynaecomastia and supraclavicular lymphadenopathy. Testicular examination identified a left testis irregularity that was confirmed on ultrasound. Chest Radiograph revealed multiple bilateral opacities measuring up to 6 cm. Initial urine HCG was negative when tested on two occasions; however given suspicion for a HCG-secreting tumour, serum HCG was measured and reported as 503,944 IU/ml (<5) and AFP 17.6 IU/ml (0-5.0). The negative urine HCG is believed to be due to "hook effect". CT revealed bulky retroperitoneal lymphadenopathy measuring 13 cm consistent with metastatic spread from the non-seminamatous germ cell tumour of testicular origin. Up front chemotherapy protocol with 4 cycles cisplatin based therapy was initiated given his disease burden and degree of symptoms. Radical orchidectomy was deferred until after chemotherapy - at which time germ cell tumour was only identified on immunohistochemistry staining. Over the 2 months following chemotherapy, all endocrinopathies resolved with corresponding reduction of HCG to 65.0 IU/ml. Symptoms of hyperthyroidism abated with treatment and his TFTs were biochemical normal. Oestrogen level also normalised with treatment. HCG-induced hyperthyroidism is a rare cause of hyperthyroidism. Endocrine manifestations occur in <5% germ cell tumour presentation but should be considered particularly when multiple endocrine abnormalities are present.