Growth Hormone Replacement Therapy in Veterans With Mild Traumatic Brain Injury (mTBI) and Adult Growth Hormone Deficiency (AGHD)

Inclusion Criteria: * OEF/OIF/OND Veteran * Score of 18 or more on Combat Experiences sub-scale of Deployment Risk and Resilience Inventory-2 (DRRI-2) * Age 21 - 55 years old * One or more mTBI sustained during military service at least 12 months prior to the screening date, as noted via the CRAFT survey * GH deficiency diagnosed by: macimorelin stimulation test (cut point 5.1 mcg/L) and IGF-I lab values have to be less than or equal to +1 SDS at baseline * Score of 11 or more on QoL-AGHDA * 4-week stability on any psychotropic medications * 3-month stability on all other hormone treatments * Able and willing to provide informed consent to participate in this study, and complete study protocol. Exclusion Criteria: * History of moderate or severe TBI * History of neurologic disorder other than TBI with substantial impact on quality of life * History of bipolar disorder, schizophrenia, or other concurrent psychotic disorder * Active suicidal ideation (no plan required) as determined by a score of 2 points or more on the Columbia Suicide Severity Rating Scale (C-SSRS) suicidal ideation rating, or overt suicidal behavior in the past 6 months * Contraindication to rhGH therapy * Contraindication to macimorelin use, including QTc interval \>470ms * Acute medical illness, active infection, cancer or decompensated chronic medical illness * Evidence of substance use disorder, -other than mild alcohol or cannabis use disorder-, or urine toxicology evidence of the use of an illicit drug (excluding cannabis), in the past 6 months. Nicotine use is allowed. * Score less than or equal to 41 on Trial 2 or Retention Trial of the Test of Memory Malingering (TOMM). * BMI \> 35 or body weight \> 350 lbs * Pituitary anatomy documented by an MRI using a sella protocol within the last 2 years indicating abnormalities consistent with an etiology other than mild-TBI (i.e.; pituitary mass) * Women who are pregnant or of child-bearing potential not on contraception * Current use of the following: growth hormone, estrogen or estrogen-like dietary supplements, progestin, IGF-I, or chronic glucocorticoid use in supraphysiologic doses * Currently enrolled in any other interventional study unless prior approval is provided by the study chairs and the study sponsor (Cooperative Studies Program)