FIG. 4.

Scatter plot of serum testosterone (T) and luteinizing hormone (LH) by age in the traumatic brain injury (TBI) cohort. Linear regression for (A) 1–6 month average T levels. Also graphed are mean T levels for our healthy controls (16.64 nmol/L) and our clinical laboratory low-normal reference level (10 nmol/L). (B) 1–6 month average LH levels compared with age for men with TBI. There was a significant reduction in serum T with older age (p = 0.0001) but only a trend for increases in LH with older age (p = 0.0521). Also graphed are mean LH (4.82 IU/L) for healthy controls and high normal reference level for our clinical laboratory (5.6 IU/L).