When a blast rattles the brain, the resulting concussion sometimes leads to unremitting psychological problems such as depression, anxiety, irritability, sleep disorders, pain, and learning and memory problems. Tens of thousands of American veterans are estimated to suffer from this postconcussive syndrome (PCS), formerly associated with shell shock. Now evidence suggests that a hormone imbalance may underlie the chronic symptoms—meaning hormone replacement therapy could spur a dramatic recovery.

At least since World War I, scientists have tried to figure out why about 10 percent of adults' concussions—from any cause, including accidents, falls and sports injuries—lead to persistent psychological and physical complaints. Endocrinologist Charles Wilkinson of the VA Puget Sound and the University of Washington and his colleagues were intrigued by studies that found pituary hormone deficiencies, which affect only 1 percent of the general population, in many people who had had a concussion. No one had investigated whether a blast concussion could disrupt hormones as well, so Wilkinson's team tested 35 soldiers who had been near a bomb explosion. They found that a whopping half of the soldiers had undergone a precipitous drop in growth and sex hormones compared with other deployed soldiers without any concussions. The data were presented in April at the Experimental Biology 2013 meeting in Boston.

The researchers hypothesize that the force of a blast physically disrupts the pituitary gland's ability to either produce or transport its hormones. Receptors for growth hormone and its by-product hormone IGF-1 are found throughout the brain. The receptors' locations—in areas such as the amygdala, prefrontal cortex, putamen and hippocampus—correspond with functions that are disturbed in PCS, including mood, sleep and memory. In addition, hormones are thought to affect plasticity, maintenance and protection of the brain. Wilkinson and his colleagues plan to test soon whether hormone replacement therapy could benefit patients with PCS—he is optimistic because such therapy has been shown to improve the same symptoms in people with hormone deficiencies from other causes. “There is considerable evidence that the cognitive and mood problems of growth hormone deficiency can be treated successfully with growth hormone replacement,” Wilkinson says.