The aim of this study is to assess if hypogonadic men with periodontitis benefit from testosterone replacement therapy before being submitted to periodontal treatment. Fifty hypogonadic men (Total Testosterone <200ng/dL) will be recruited from the Clinics Hospital at Federal University of Paraná and subjected to periodontal evaluation by a trained and calibrated researcher. The subjects presenting with periodontitis (assessed by clinical parameters) will be randomly allocated to "testosterone replacement therapy" (TRT) group or "placebo" for 3 months. After that time, all patients will receive nonsurgical periodontal treatment, which will be reassessed after 45 days. Clinical parameters (such as probing depth, gingival and plaque index, clinical attachment loss, bleeding on probing), sub gingival plaque and gingival crevicular fluid will be collected at baseline, just before therapy and 45 days after therapy.