To the Editor Reinisch et al1 recently reported a randomized clinical trial evaluating the efficacy of endocrine therapy in treating breast cancer in men. Their primary objective was to compare changes in estradiol concentrations within 3 treatment arms; their secondary objectives included measuring changes in concentration of several hormonal biomarkers. Although we greatly appreciate the authors’ efforts to perform this study, we were surprised and disappointed by the absence of any information on the analytical methods used to measure the hormone concentrations. The method used to quantify any biomarker, and especially hormones, can significantly affect study outcome and replication.2 Analytical methods may differ in accuracy of the obtained test results, sensitivity and specificity for the biomarker, analytical traceability, and standardization required for translation to other methods.2 Therefore, adequate reporting of the analytical method used is essential if the obtained results are to be properly assessed and replicated.