Chronic Hypopituitarism Associated with Increased Postconcussive Symptoms Is Prevalent after Blast-Induced Mild Traumatic Brain Injury

Abstract

The most frequent injury sustained by US service members deployed to Iraq or Afghanistan is mild traumatic brain injuries (mTBI), or concussion, by far most often caused by blast waves from improvised explosive devices or other explosive ordnance. TBI from all causes gives rise to chronic neuroendocrine disorders with an estimated prevalence of 25-50%. The current study expands upon our earlier finding that chronic pituitary gland dysfunction occurs with a similarly high frequency after blast-related concussions. We measured circulating hormone levels and accessed demographic and testing data from two groups of male veterans with hazardous duty experience in Iraq or Afghanistan. Veterans in the mTBI group had experienced one or more blast-related concussion. Members of the deployment control (DC) group encountered similar deployment conditions but had no history of blast-related mTBI. 12 of 39 (31%) of the mTBI participants and 3 of 20 (15%) veterans in the DC group screened positive for one or more neuroendocrine disorders. Positive screens for growth hormone deficiency occurred most often. Analysis of responses on self-report questionnaires revealed main effects of both mTBI and hypopituitarism on postconcussive and posttraumatic stress disorder (PTSD) symptoms. Symptoms associated with pituitary dysfunction overlap considerably with those of PTSD. They include cognitive deficiencies, mood and anxiety disorders, sleep problems, diminished quality of life, deleterious changes in metabolism and body composition, and increased cardiovascular mortality. When such symptoms are due to hypopituitarism, they may be alleviated by hormone replacement. These findings suggest consideration of routine post-deployment neuroendocrine screening of service members and veterans who have experienced blast-related mTBI and are reporting postconcussive symptoms.

Keywords: blast; concussion; growth hormone deficiency; military; pituitary; posttraumatic stress disorder; traumatic brain injury; veterans.

Figure 1

Concentration of insulin-like growth factor (IGF-I) in serum of deployment control (DC) (circles) and mild traumatic brain injuries (mTBI) (triangles) participants as a function of age. The criterion for a positive screen for growth hormone is an IGF-I level below the age-adjusted 10th percentile of IGF-I concentration (diagonal line) in the community control reference group. Serum IGF-I values of six of the mTBI group () and two of the DC group () fell below the cutoff line.

Figure 2

Mean scores of each participant group on each item of the neurobehavioral symptom inventory. T-bars indicate SEMs. The higher the score, the greater the frequency or severity of the symptom endorsed. All symbols indicate a significant main effect of participant group on that self-report item by one-way analysis of variance (ANOVA). Significant group effects were found by one-way ANOVA on 15 of 22 items. Each symbol represents a specific result of post hoc Tukey HSD tests. No significant paired comparisons by Tukey HSD. Significant difference between mTBI-HP and DC-N by Tukey HSD. Significant difference between mTBI-HP and DC-HP by Tukey HSD. Significant difference between mTBI-N and DC-HP by Tukey HSD.