Fatigue is a common symptom after traumatic brain injury that can be an indirect result of other common TBI symptoms (such as depression, pain, or sleep disturbance) or a direct result from pituitary gland damage and its resulting hormonal dysfunction. Growth hormone deficiency, testosterone deficiency, or adrenal insufficiency are types of hormonal dysfunctions that are known to be related to fatigue. It has been increasingly clear that pituitary damage is more common in TBI than previously thought. It was therefore assumed that hormonal dysfunction could be responsible for much of the fatigue experienced by TBI patients.
However, when comparing the symptoms of traumatic brain injury, a recent study found that hormonal dysfunction was not as strongly correlated with fatigue as other fatigue-related symptoms. The study found that the strongest predictors of fatigue were: being female, suffering from depression or pain, and having memory deficits.
Englander J, Bushnic T, Oggins J, & Katznelson L. Fatigue after traumatic brain injury: Association with neuroendocrine, sleep, depression and other factors. Brain Injury. (November 2010).