Charactertizing Growth Hormone Deficiency in Traumatic Brain Injury

The goal of this observational study is to characterize the impact of growth hormone deficiency (GHD) on quality of life, symptom burden, and sleep in adults with traumatic brain injury (TBI), and to evaluate whether these outcomes improve with growth hormone replacement therapy. The main questions it aims to answer are: * Does quality of life, as measured by the Quality of Life Assessment of Growth Hormone Deficiency in Adults (QoL-AGHDA), differ between adults with TBI and GHD compared to those with TBI and no GHD? * Do fatigue, cognition, mood, post-concussion symptoms, body image, libido, perceived stress, and sleep architecture differ between these two groups? * Among participants with GHD who begin growth hormone replacement therapy, do symptom burden and quality of life improve over a 12-week treatment period? Eligible participants will be asked to complete baseline questionnaires and undergo testing for growth hormone deficiency (glucagon stimulation testing). A subset of participants will also complete objective sleep assessments using actigraphy and at-home polysomnography. For those who are diagnosed with growth hormone deficiency and choose to pursue treatment, questionnaires will be repeated bi-weekly while receiving growth hormone replacement therap