RecruitingEarly Phase 1Drug trialTestosterone and Neural FunctionSpinal cord injury (SCI) disrupts the nerves controlling movement, along with those that regulate functions like heart rate and blood pressure (known as the autonomic nervous system, or ANS). Testosterone (T) plays a significant role in brain health and ANS reflex function in non-neurologically impaired men. However, little is known about the relationships between T, nerve function, and ANS dysfunction after SCI. Interestingly, up to 60% of men with SCI exhibit persistently low T concentrations, which may worsen nerve and ANS dysfunction. In uninjured eugonadal people (normal physiologic range of serum T concentrations), a single pharmacologic dose of intranasal T has been shown to quickly improve nerve function, but no study has evaluated if T administration alters nerve and ANS function in men with SCI. Herein, the investigators will conduct the first study to test how a single dose of intranasal T impacts motor and ANS function in this population.