Chronic Hypopituitarism after Blast Concussion Mild Traumatic Brain Injury in Iraq/Afghanistan Combat Veterans

Endocr Rev, Vol. 32 (03_MeetingAbstracts): OR16-4
Copyright © 2011 by The Endocrine Society

Charles W Wilkinson, PhD², Elaine R Peskind, MD², Elizabeth A Colasurdo² and Jane B Shofer, MS¹

Department of Psychiatry and Behavioral Sciences (JBS), University of Washington, Seattle, WA
Geriatric Research, Education and Clinical Center (CWW,ERP,EAC), Veterans Affairs Puget Sound Health Care System, Seattle, WA

Studies of civilian traumatic brain injury (TBI) from all causes have found evidence of chronic hypopituitarism, as defined by deficient production of one or more pituitary hormones measured at least one year after injury, in 33-50% of cases (1). Its occurrence has not been found to be related to trauma severity (1,2). Hypopituitarism is associated with non-specific behavioral symptoms that can be mistaken for PTSD, including fatigue, anxiety, depression, irritability, insomnia, poor concentration and memory, and decreased quality of life (1). Despite these findings, the prevalence of hypopituitarism after blast concussion mild TBI, the signature injury of combat in Iraq and Afghanistan, has not yet been investigated. Mild TBI (mTBI) is characterized by brief loss of consciousness or loss of memory for events surrounding the trauma or any alteration of mental state (disorientation, confusion). In order to determine the frequency of pituitary dysfunction after blast concussion mTBI, we are measuring pituitary and target organ hormones in blood samples from Iraq/Afghanistan Veterans with mTBI taken at least one year subsequent to their last blast exposure. Most have experienced multiple blast exposures. Criteria for identifying abnormal circulating levels of LH, FSH, total testosterone, prolactin, ACTH, cortisol, TSH, free thyroxine, GH, IGF-I, and arginine vasopressin (AVP) were derived from RIA or EIA measurement of basal morning concentrations in a large group of male non-Veteran control subjects. In general, values below the 5th percentile or above the 95th percentile were defined as abnormal. When both pituitary and target organ hormones were measured for a given axis, a specific combination of criteria signaled dysfunction of that axis. Using the criteria defined in controls, 10 of 26 Veterans with blast mTBI were found to have abnormal hormone levels in one or more pituitary axes. Seven mTBI subjects exhibited deviant plasma AVP concentrations, either above or below the 5th-95th percentile normal range. The frequency of abnormally low or abnormally elevated AVP levels has been found to be relatively high in the acute stage of non-blast TBI, but it tends to decline with time. These preliminary findings suggest that the prevalence of hypopituitarism after blast concussion mTBI is similar to that in other forms of TBI, and that recovery and rehabilitation of blast-exposed Veterans may be facilitated by comprehensive screening for pituitary dysfunction.

(1) Ghigo E et al., Brain Inj, 2005; 19:711(2) Lieberman SA et al., J Clin Endocrinol Metab 2001; 86:2752

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