Testicular choriocarcinoma: an unusual case of paraneoplastic thyrotoxicosis

Abstract

The incidence of clinical hyperthyroidism has been reported as 0.8/1000 women per year, and it is less common in men.1 Causes of thyrotoxicosis include Grave’s disease, toxic multi-nodular goitre, toxic adenoma and thyroiditis. Rarely, thyrotoxicosis can arise as a paraneoplastic syndrome. In this setting, systemic symptoms of underlying malignancy may be wrongly attributed to primary hyperthyroidism leading to a delay in diagnosis. We report a rare case of thyrotoxicosis due to metastatic testicular choriocarcinoma that highlights the importance of a systematic clinical and biochemical assessment. An 18-year-old male catering student initially presented to his family practitioner with back pain and dysuria and was diagnosed with a urinary tract infection. He was empirically prescribed two consecutive courses of antibiotics. He then developed a cough and dyspnoea attributed to community acquired lower respiratory tract infection, which was treated. His condition continued to deteriorate with a weight loss of 13.6 kg over a 6-week period. During this time, he had developed a large right testicular swelling, which was concealed. Routine thyroid function tests revealed a raised serum free thyroxine level and reduced thyroid-stimulating hormone (TSH) concentrations [free thyroxine 38.6 pmol/l (normal range (NR) 9.4–18.6), TSH <0.01 mu/l (NR 0.3–4.4)]. A few days later, he presented to our Emergency Department with haemoptysis. His past medical history was non-contributory and he had been prescribed no regular medications. He had stopped smoking 3 weeks prior to presentation.