Inclusion Criteria:
* Veterans eligible for care within the Veterans Health Administration (VHA)
* Diagnosis of motor incomplete SCI (AIS C-D) for \>24-months involving spinal segment lumbar (L)1 or above from trauma, vascular, or orthopedic pathology
* Low total testosterone (\<300 nanograms/decilliter \[ng/dL\]) and/or low free testosterone (\<4.6 ng/dL)
* Presence of one or more sign of low testosterone, defined as:
* decreased energy
* motivation
* initiative or self-confidence
* increased fatigue or tiredness
* reduced sexual desire or activity
* decreased spontaneous (e.g., morning) erections or erectile dysfunction
* loss of body hair or reduced shaving
* feeling sad or blue or having a depressed mood or a persistent low-grade depressive disorder (defined as a score of \>3 on the Patient Health Questionnaire \[PHQ\]-2)
* hot flashes
* fatigue or irritability
* poor concentration or memory
* mild unexplained (normocytic-normochromic) anemia, defined as hematocrit (HCT) \<40%, hemoglobin \<13.6 grams/deciliter (g/dL), or red blood cell count \<4.5 million/microliter (mcL)
* sleep disturbances or increased sleepiness
* reduced muscle bulk, strength, or physical function
* increased body fat or body mass index
* Presence of motor impairment, defined as self-selected walking pace ≤1.0 meters/second (m/s) on a 10-meter walk test (10mWT), with or without gait devices or braces and with or without assistance from another person, or as self-selected walking pace \>1.0 m/s with reliance on a gait device or brace or with highly compensated movement impairment identified by a trained observer
* Medically stable condition asymptomatic for bladder infection, major decubiti, cardiopulmonary disease, or other significant condition that will interfere with the study
* Documented approval from a physician verifying medical status
Exclusion Criteria:
* Involvement in another research study that may influence outcomes
* Mental state that precludes understanding the protocol
* Life expectancy \<12 months
* History of or current congenital spinal cord injury (SCI) (e.g., Chiari malformation, myelomeningocele, intraspinal neoplasm, Friedreich's ataxia) or degenerative spinal disorder (e.g., spinocerebellar degeneration) that may complicate procedures
* Amyotrophic lateral sclerosis, multiple sclerosis, or other neurologic injury / impairment that may complicate procedures
* Current cancer diagnosis
* History of prostate or breast cancer
* Any diagnosed or treated cancer in the past 24 months, except basal or squamous cell carcinoma of the skin that has been successfully treated
* Any major lower-limb fracture in the past 12 months
* Unevaluated circulating prostate-specific antigen (PSA) \>4.0 nanograms/milliliter (ng/mL) or \>3.0 ng/mL in men with prostate cancer risk factors, including agent orange exposure, first degree relative with prostate cancer, or African American background
* Currently seeking fertility or expected during the study
* Diagnosed gynecomastia
* Hematocrit (HCT) \>48%
* Any major cardiovascular event in the last 6 months, defined as:
* an acute myocardial infarction
* any cardiac revascularization procedure including stenting
* angioplasty or coronary artery bypass grafting
* revascularization of the carotid or middle cerebral artery or procedure to treat critical limb ischemia
* hospitalization due to unstable angina
* transient ischemic attack
* stroke
* peripheral vascular disease
* Any angina that is not controlled on a current medical regimen (Canadian class II, III, or IV)
* Poorly compensated congestive heart failure (New York Heart Association \[NYHA\] class III or IV)
* Poorly controlled hypertension when on medication (consistent systolic BP ≥160 mmHg or diastolic BP ≥100 mmHg)
* Poorly controlled arrhythmia of any type
* Severe valvular heart disease
* Baseline electrocardiogram findings such as left bundle branch block or marked abnormality that precludes serial screening for occult ischemic events
* History of unprovoked deep venous thrombosis, unprovoked pulmonary embolism, history of recurrent deep venous thrombosis or known thrombophilia
* Major non-cardiovascular surgery (e.g., major abdominal or thoracic procedure) within 90 days before screening or a major surgery scheduled at the time of screening
* Liver enzymes (aspartate aminotransferase \[AST\] or alanine aminotransferase \[ALT\]) \>1.5 times the normal upper limit
* Severe or end-stage chronic kidney disease defined as eGFR \<30 milliliters/minute (mL/min)
* Diagnosed, but untreated severe obstructive sleep apnea
* Use of an agent that alters sex-steroid metabolism in the past 90 days, such as: testosterone therapy (TRT), compounded or over-the-counter androgenic hormone or androgen precursor, 5-alpha reductase (5AR) inhibitors, growth hormone, clomiphene, aromatase inhibitors, anti-estrogen or estrogen treatment, or others
* Use of anti-resorptive or bone anabolic drug therapy in the past 180 days
* Acute use (\>5 days) of any opioid (e.g., oxycodone, hydrocodone) or systemic glucocorticoids \>7.5 milligrams (mg)/day prednisone equivalent (e.g., hydrocortisone 30 mg, methylprednisolone 6 mg, or dexamethasone 1.2 mg) in the week before screening, except for men who are taking these for a chronic condition and who are anticipated to continue these for the study duration
* Known allergy to any TRT component (e.g., cottonseed oil or other)
* Any other condition, lab abnormality, therapy, medical or psychiatric condition, or reason that might pose a risk to the participant, make participation not in the person's best interest, confound the study results (e.g., inability to comply with study requirements), make the participant unsuitable to receive a study intervention, or interfere with their ability to participate for the full study duration