The purpose of this study is to determine whether growth hormone replacement therapy (GHRT) is effective versus placebo in the improvement of Quality of Life in patients with adult growth hormone deficiency (AGHD) and mild traumatic brain injury (mTBI).

Inclusion Criteria:

1. OEF/OIF/OND Veteran
2. Score of 18 or more on Combat Experiences sub-scale of Deployment Risk and Resilience Inventory-2 (DRRI-2)
3. Age 21 - 55 years old
4. One or more mTBI sustained during military service at least 12 months prior to the screening date, as noted via the CRAFT survey.
5. GH deficiency diagnosed by: macimorelin stimulation test (cut point 5.1 mcg/L), or glucagon stimulation test (cut point: 3 mcg/L for BMI up to 25; cut point 1 mcg/L for BMI 25 and above) and IGF-I lab values have to be less than or equal to +1 SDS at baseline
6. Score of 11 or more on QoL-AGHDA
7. 4-week stability on any psychotropic medications
8. 3-month stability on all other hormone treatments
9. Able and willing to provide informed consent to participate in this study, and complete study protocol.

Exclusion Criteria:

1. History of moderate or severe TBI
2. History of neurologic disorder other than TBI with substantial impact on quality of life
3. History of bipolar disorder, schizophrenia, or other concurrent psychotic disorder
4. 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.
5. Contraindication to rhGH therapy
6. Acute medical illness, active infection, cancer or decompensated chronic medical illness
7. 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.
8. Score less than or equal to 41 on Trial 2 or Retention Trial of the Test of Memory and Malingering (TOMM).
9. BMI > 40 or body weight > 350 lbs
10. 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)
11. Women who are pregnant or of child-bearing potential not on contraception
12. Current use of the following: growth hormone, estrogen or estrogen-like dietary supplements, progestin, IGF-I, or chronic glucocorticoid use in supraphysiologic doses
13. Currently enrolled in any other interventional study unless prior approval is provided by the study chairs and the study sponsor (Cooperative Studies Program)

Digital data underlying primary scientific publications from this study will be held as part of a data sharing resource maintained by the Cooperative Studies Program (VA-CSP). These data may be available to the public and other VA and non-VA researchers under certain conditions and consistent with the informed consent and CSP policy which prioritize protecting subjects' privacy and confidentiality to the fullest extent possible.