Hypoxic stress: A risk factor for post-concussive hypopituitarism?

Hypopituitarism diagnosed months or years following concussive injury can cause a variety of endocrine disturbances including insufficient secretion of human growth, luteinizing, follicle stimulating, thyroid stimulating, adrenocorticotrophic, and antidiuretic hormones. Recent evidence suggests that autoimmune reactions against pituitary and/or hypothalamic tissue constitute an etiologic factor for this hypopituitarism. One important trigger for autoimmunity is hypoxic stress. This trigger may be especially important in the post-concussive brain, which is particularly vulnerable to hypoxic stress. The vulnerable vasculature of the hypothalamic infundibulum can be a source of local exacerbation of any systemic hypoxia. Taking the above into account, it seems reasonable to hypothesize that hypoxic stress is a risk factor for post-concussive hypopituitarism. Following a discussion of literature relevant to this hypothesis, we suggest retrospective and prospective research methods for testing the hypothesis. Retrospective methods for hypothesis testing include comparing post-concussion victims with and without evidence of hypopituitarism in terms of their history of respiratory problems such as smoking, exposure to indoor and outdoor air pollution, chronic obstructive pulmonary disease, asthma, obstructive sleep apnea, and opioid use or abuse. Significantly greater incidence of respiratory history among the hypopituitarism patients would support the hypothesis. Prospective methods include performing detailed respiratory history and examination immediately post-injury, then performing periodic endocrine panels to detect hypopituitarism during long-term follow up. The hypothesis will be supported if development of hypopituitarism among patients with positive respiratory history or examination findings post-injury is more frequent than hypopituitarism among concussion victims with negative respiratory history and exam findings. If the hypothesis is supported, effective prevention of post-concussive hypopituitarism should include efforts to support optimal respiratory function. Such efforts may be relevant to treatment as well. These efforts would include respiratory therapy, smoking cessation, treatment of obstructive sleep apnea, prudent stepping down of opioid use, incentive spirometry, aerobic exercise, and other conventional measures as indicated. Non-Western measures such as yoga should be considered as well. In addition, chiropractic care as an intervention that may ameliorate hypoxia at the systemic and local levels is discussed.