Impact of GHRH on Sleep Promotion and Endocrine Regulation in Service Members Who Sustained a Traumatic Brain Injury and Have Current Insomnia

Objective: Traumatic brain injury (TBI) is the hallmark injury of deployment in Iraq and Afghanistan. Up to one-third of service members who sustain a TBI are diagnosed with a sleep disorder; insomnia being one of the most common. Currently, over half of TBI-associated insomnia cases remain untreated due to poor efficacy of available pharmacologic agents. Neuroendocrine dysfunction is an important mechanism linking TBI and disordered sleep, thus pharmacological agents that address this dysfunction may be effective in treating TBI-related insomnia. The neuroendocrine system is essential for regulating sleep and circadian function. Decreased neuroendocrine function, including the hypothalamus and the somatotrophic cells of the anterior pituitary, which regulate growth hormone secretion, likely contributes to insomnia. This assertion is supported by previous studies that demonstrated the sleep-promoting effects of growth hormone releasing hormone (GHRH) administration in healthy controls, the elderly, and participants with depression. Therefore, we propose that administration of GHRH will address the underlying mechanisms of insomnia in service members and veterans who sustained a TBI, and provide a pharmacological agent more robust than currently available treatments. Study population: This study will recruit 50 active duty service members and veterans with a documented TBI to participate in one of two study groups. The insomnia group (n=25) will include participants that have a current clinical diagnosis of insomnia without obstructive sleep apnea. The no-insomnia group (n=25) will include participants with no current clinical diagnosis of insomnia or obstructive sleep apnea. Withdrawals/dropouts will be replaced to obtain 20 participants per group who complete the study. Design: A double-blind, randomized, crossover design will be used to examine the impact of tesamorelin (GHRH (1-44) analog) or placebo on total non-rapid eye movement (NREM) time evaluated during two polysomnography visits, scheduled 1-3 weeks apart. Serial blood draws will be obtained during the polysomnography to examine endocrine function and neuropeptide release. Outcome measures: The primary outcome is change in NREM time following tesamorelin administration compared to placebo. The secondary outcomes are (1) within and between group differences in plasma concentration levels of neuroendocrine proteins following tesamorelin administration compared to placebo and (2) within and between group differences in urinary concentration levels of growth hormone following tesamorelin administration compared to placebo.