Testosterone And Vitamin D Concentrations In Military Personnel Following Traumatic Brain Injury

Background: Traumatic brain injury (TBI) has been shown to cause pituitary dysfunction, manifesting in low testosterone concentrations, and previous research suggests a link with vitamin D deficiency.Purpose: To compare testosterone and vitamin D concentrations in service members with and without a TBI, and to identify the frequency of testosterone prescriptions.Materials and methods: This retrospective de-identified medical review analysed assessments (testosterone, vitamin D) ordered for 4285 active duty and veteran military personnel at Womack Army Medical Center, Fort Bragg, NC from 2016-2018.Results: Overall, 343 (8%) of service members had a medically diagnosed TBI. In all men, 19% were deficient in testosterone (<270 ng/dl), and 10% had a testosterone prescription. Active duty men with TBI history had lower testosterone than active duty men with no documented head injury (431 +/- 162 vs 452 +/- 170 ng/dl, P = 0.04). However, there was no significant difference in veteran men. More than one-third (38%) of all service members were insufficient in vitamin D (<30 ng/ml). Overall there was a weak positive correlation between testosterone and vitamin D concentrations in men but not in women.Conclusions: Our research does not support evidence for high rates of hypogonadism, testosterone prescription, or vitamin D deficiency after TBI compared to military personnel without prior injury. However, we found a high prevalence of vitamin D insufficiency in active duty and retired service members independent of TBI, further supporting that vitamin D status should be assessed regularly in service members.