Testicular germ cell tumour presenting as thyrotoxicosis

Abstract

Testicular germ cell tumour presenting as thyrotoxicosisWe wish to raise four important points regarding the diagnosis, aetiology and management of beta human chorionic gonadotropin (bhCG)-induced hyperthyroidism. 1 1. bhCG-induced hyperthyroidism is characterized by very high levels of bhCG and these may cross-react in some TSH assays, 2,3 giving apparently normal rather than suppressed TSH values. Since many laboratories o¡er TSH as the ¢rst-line test in investigating thyroid dysfunction, the diagnosis of bhCGinduced hyperthyroidism may be missed.2. bhCG exists as several isoforms dependent on carbohydrate content. Desialated isoforms, which are produced more abundantly in cases of bhCG-induced hyperthyroidism, have greater thyrotrophic activity than the more common sialated isoforms. 4,5 Therefore, the quality rather than the quantity of bhCG is important in the development of bhCG-induced hyperthyroidism. This also explains why the very high bhCG levels in pregnancy are not usually associated with thyrotoxicosis.3. The most common and often the only presenting sign of bhCG-induced thyrotoxicosis in men is tachycardia, 2,6,7 as exempli¢ed in this case. Other features include very high oestradiol concentrations with gynaecomastia and the presence of widespread metastatic disease. 2,6,7 4. Tumour bhCG-induced hyperthyroidism may require standard anti-thyroid treatment, but almost invariably responds to e¡ective tumour chemotherapy. Tumour relapse may also be associated with recurrence of the thyrotoxicosis. 2