Reassessment of the definition of castrate levels of testosterone: Implications for clinical decision making

Objectives. Based on methods introduced in the late 1960s and no longer used, serum testosterone level in men after surgical castration was reported to be 50 ng/dL or less. Radioimmunoassay and, subsequently, chemiluminescent methods have supplanted the early analytic methods because of their improved accuracy and ease of testing. The purpose of this study was to define the castrate testosterone level in the era of chemiluminescent testing. Methods. After bilateral orchiectomy, serum testosterone (total) levels were measured prospectively in 35 prostate cancer patients. Results. The median testosterone value in this patient cohort was 15 ng/dL (0.5 nmol/L; 95% confidence interval 12 to 17 ng/dL). Conclusions. In a contemporary series, castrate testosterone should be defined as less than 20 ng/dL (0.7 nmol/L). The important biologic and economic implications are discussed. UROLOGY 56: 1021-1024, 2000. (C) 2000, Elsevier Science Inc.