Growth Hormone or Sildenafil as Therapies for Fatigue in Mild- Traumatic-brain-injury (MTBI)

Three primary outcome measures are proposed: 1. Perceptual fatigue as measured weekly using the Brief Fatigue Inventory (BFI) (59). 2. Performance fatigue as measured at baseline and month 3, 6 and 12 using hand and leg dynamometry. 3. Neuropsychological function as measured at baseline and month 12. Secondary outcomes will include: 1. Modified 6 minute walk performance as measured at baseline, and month 3, 6 and 12. 2. Mood and quality of life using the Profile of Mood States, Quality of Life Assessment of GH Deficiency in Adults questionnaire, and a grief assessment (60) (POMS), measured at baseline, and month 3, 6, and 12. 3. Sleep quality using the Pittsburgh Sleep Quality Index (PSQI), baseline, and month 3, 6, and 12. 4. Multidimensional fatigue using Multidimensional Fatigue Symptom Inventory (MFSI) at baseline, and month 3, 6 and 12. 5. Skeletal muscle mass, as derived from lean body mass determinations, using dual energy X-ray absorptiometry (iDEXA) at baseline, and month 3, 6, and 12. 6. Physical Activity, measured daily using accelerometry. 7. Cerebral blood oxygen saturation measured at baseline and month 12. 8. Leg blood flow measured at baseline, and month 3, 6 and 12. 9. Blood Hormones at baseline and month 3, 6 and 12. 10. Characterization of brain tissue using structural, "resting state" and diffusion functional MR at baseline and month 3, 6, and 12. 11. Indirect calorimetry measured at baseline and month 3, 6 and 12.