ABSTRACT Introduction: The main cause of slightly elevated human chorionic gonadotropin (HCG) after successful treatment of male germ cell tumors is considered to be pituitary-derived HCG. It is well known that pituitary-derived HCG is frequently detected in postmenopausal women. We evaluated the status of serum HCG in men with elevated gonadotropins, which were induced by androgen deprivation therapy, using commercially available assays. Materials and Methods: We enrolled 44 patients with prostate cancer, who underwent luteinizing-hormone releasing hormone agonist treatment. We measured serum follicle-stimulating hormone (FSH), serum luteinizing hormone (LH), serum total HCG, serum free HCG-β subunit, and urine total HCG 3 times per patient, on the day of treatment initiation, the next day, and 3 months after. Results: On the day after treatment initiation, serum and urine HCG was detected in 61% and 73% of patients, respectively. Markedly strong correlations were observed between serum/urine HCG and FSH/LH. In particular, receiver operating characteristic curve analysis indicated excellent area under the curve (0.977, 95% confidence interval 0.951–1.003)) for serum HCG-detectable LH. At the cutoff value of 21.07 mIU/mL for serum HCG-detectable LH, the sensitivity and specificity were 96.7% and 95.3%, respectively. Serum HCG-β was not detectable at any times in any patients. Conclusions: Suggested pituitary-derived HCG can be frequently detected in patients with elevated gonadotropins, and there is a firm association between HCG detection and gonadotropin levels.