Prevalence of paraneoplastic hyperthyroidism in patients with metastatic non-seminomatous germ-cell tumors.

Background: Patients with elevated human chorionic gonadotrophin (HCG) can have hyperthyroidism. We assessed the prevalence of hyperthyroidism in patients presenting with disseminated non-seminomatous germ-cell tumors (NSGCT).
Patients and Methods: In all patients with metastatic NSGCT who started chemotherapy at our center from April 2001 to April 2007, thyroid function was analyzed. The association between thyroid function and HCG level was examined and the frequency of hyperthyroidism in patients with low (<5000 IU/l), intermediate (> or = 5000 but <50 000 IU/l) and high (> or = 50 000 IU/l) serum HCG was assessed.
Results: For 144 of 148 eligible patients, thyroid function tests were available. Five patients with hyperthyroidism (3.5%) were identified, who all had high-serum HCG (mean 1 325 147 IU/l). Fifty percent of the patients with high HCG levels had hyperthyroidism versus 0% of the patients with HCG <50 000 IU/l (P < 0.001). Free thyroxin levels normalized within 26 days after starting chemotherapy in all patients.
Conclusions: Hyperthyroidism frequently accompanies NSGCT with highly elevated HCG. Since its symptoms overlap with those of extensive metastatic disease, it may not be recognized. Thyroid function should be assessed in patients with high HCG levels and symptomatic hyperthyroidism should be treated temporarily with beta-blockade or antithyroidal medication.