Pain Alleviation With Testosterone in Opioid-Induced Hypogonadism

Inclusion Criteria: * Men, age 18 years and older. * Chronic non-cancer spinal pain. * Use of opioid analgesics for at least 6 months. * Serum total testosterone (measured by mass spectrometry) \<348 ng/dL and/or free testosterone \<70 pg/mL. * Ability and willingness to provide informed consent. Exclusion Criteria: * History of prostate cancer or breast cancer. * Known history of organic hypogonadism (e.g., due to hypothalamic, pituitary or testicular disease). * Use of testosterone within the past 6 months. * Baseline hematocrit \>48%. * Prostate-specific antigen (PSA) level \>4 ng/mL in Caucasians or \>3 ng/mL in African-Americans. * Presence of prostate nodule or induration on digital rectal examination. * Uncontrolled congestive heart failure. * Myocardial infarction, acute coronary syndrome, revascularization surgery or stroke within 3 months. * Serum creatinine \>2.5 mg/dL. * Alanine aminotransferase (ALT) level 3 times above the upper limit of normal. * Diagnosis of bipolar disorder or schizophrenia. * Presence of metallic implants (pacemakers, aneurysm clips, etc.) that preclude the patient from undergoing functional magnetic resonance imaging (MRI). In subjects who are otherwise eligible and either do not qualify for MRI or are reluctant to undergo imaging, the investigators may consider enrolling such participants on a case-by-case basis.