Prevalence of post-traumatic hypopituitarism in active-duty service members receiving comprehensive care for traumatic brain injury (TBI) and psychological health: A military mild TBI cohort study.

Objective: The prevalence of neuroendocrine dysfunction (NED) following mild traumatic brain injury (mTBI) remains obscure, with widely varying prevalence estimates. This study aimed to determine prevalence of NED among central hypogonadism, central hypothyroidism, and growth hormone deficiency (GHD) in active-duty military service members (SMs) receiving comprehensive TBI and psychological health care and characterize TBI burden, neurobehavioral symptom severity, and NED associations. Methods: Retrospective analysis of baseline, fasting morning serum screening labs of thyroid, gonadal, and growth hormone axes obtained from SMs attending a 4-week treatment program for TBI. NED prevalence was characterized in those who completed full tri-axis screening as well as GHD and central hypogonadism screening independently. Results: Of 1,832 TBI-screened SMs, 493 completed full neuroendocrine testing. Dual-clinician review confirmed NED in 45 (9.1%; 95% CI [6.9%, 12.0%]). Central hypogonadism (n = 33, 6.7%) was most common, followed by central hypothyroidism (n = 10, 2.0%); Screen-positive suspected GHD was 0.2% (1/493); no cases were confirmed by dynamic stimulation testing, so the true prevalence of GHD cannot be determined in this cohort. NED was associated with increased time since injury (OR = 4.15, p<.001) and fewer lifetime TBIs (OR = 0.66, p=.008), but not neurobehavioral symptoms or cognitive function. Conclusions: In the largest military TBI cohort with full NED screening to date, confirmed post-traumatic hypopituitarism prevalence was 9.1%. GHD was least common by IGF-1 (0.2%) screening, but its true prevalence remains indeterminate without systematic stimulation testing. Findings refine prevalence estimates for NED after military mTBI and emphasize the need for standardized diagnostic approaches prioritizing gonadal and thyroid axes.