Persistent hypogonadism influences estradiol synthesis, cognition and outcome in males after severe TBI

Objective: Acute hypogonadotropic hypogonadism (AHH) occurs frequently after TBI, as does chronic hypogonadotropic hypogonadism. However, AHH and persistent hypogonadotropic hypogonadism (PHH) after TBI are not well studied. The objective of this study was to characterize longitudinal hormone profiles and the impact of AHH and PHH on outcome. Methods: In this prospective cohort study, men with severe TBI (n=38) had serum gonadal and gonadotropic hormones measured during weeks 1-52 post-injury. AHH, PHH and/or early resolving hypogonadotropic hypogonadism (ERHH) were based on temporal hormone assessments. PHH and hormone profiles were then compared to multiple outcome measures 6-12 months post-TBI. Results: AHH affected 100% of the population, while 37% subsequently developed PHH. Acute testosterone (TEST) and estradiol/testosterone (E2/TEST) ratios were associated with PHH and outcome. Over time, post-acute TEST and E2 levels for the ERHH group approached normal range, while levels for the PHH group remained low. Post-acute gonadotrophin levels were within the normal range for both groups. PHH, along with lower post-acute TEST and E2 profiles, was associated with worse functional and cognitive outcomes at 6 and 12 months post-injury. Conclusions: These results support screening for post-acute secondary hypogonadism and further research to assess the mechanisms underlying PHH and associated functional and cognitive deficits.