E-Poster Presentation ESA-SRB-ANZBMS 2021

Paraneoplastic hyperthyroidism in a man with testicular cancer (#381)

Gaurav Ghosh 1 , Chanika Ariyawansa 1 , Krishnamurthy Chikkaveerappa 1
  1. Sir Charles Gairdner Hospital WA, Nedlands, WA, Australia

Introduction: Human Chorionic Gonadotropin (HCG) is a glycoprotein with a structure similar to TSH [1]. HCG-mediated hyperthyroidism from an HCG secreting tumour is a rare cause of hyperthyroidism [2].

Case: We report the case of a 29-year-old gentleman who presented with abdominal pain, tachycardia and transient atrial fibrillation. Abdominal CT revealed para-aortic retroperitoneal lymphadenopathy. Though no testicular mass was palpable, scrotal ultrasound revealed a testicular lesion suspected to be a primary tumour. Relevant tumour markers were elevated: HCG 682000 IU/L (<2), AFP 22 kIU/L (<11). Thyroid function tests (TFTs) were consistent with primary hyperthyroidism: TSH <0.01mU/L (0.4-4), T4 29 pmol/L (9-19), T3 7.3pmol/L (3-5.5). TSH receptor antibodies were 0.8 U/L (<1.8). The patient commenced propranolol for tachycardia and underwent right orchidectomy with histopathology confirming an 11 mm non-seminomatous germ cell tumour (pure teratoma of post-pubertal type). His tumour was exquisitely responsive to chemotherapy and 2 weeks after commencing chemotherapy, HCG decreased to 31200 U/L and TFTs normalised (TSH 0.83mU/L, T4 11pmol/L and T3 3.7pmol/L). Propranolol was ceased and the patient has had no recurrence of tachycardia or atrial fibrillation and has remained euthyroid on subsequent testing. Thionamides were not used at any stage.

Discussion

Germ cell tumours, particularly those of the non-seminoma type can produce substantial amounts of HCG [3]. In one study of disseminated non-seminomatous germ-cell tumours, hyperthyroidism was present in 3.5% of patients overall and 50% of those with HCG >50000 IU/L [2]. Hyperthyroidism will usually resolve with treatment of the tumour and reduction of HCG level. Hyperthyroidism can be the presenting feature of an HCG secreting tumour [3-6]. These tumours can be extra-gonadal, therefore absence of a testicular mass does not exclude the diagnosis [7]. HCG-mediated thyrotoxicosis should be considered in hyperthyroidism where another cause is not identified or in the presence of unusual clinical features [4].

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