Abstract A 49-year-old woman with a history of daily inhaled corticosteroid use for asthma presented to a concussion clinic 7 wk after sport-related head injury with headache, visual blurring, dizziness, nausea, fatigue, polydipsia, and polyuria. Examination revealed difficulty with vestibulo-occulomotor testing due to nausea and visual straining. Cranial CT/MR imaging was unremarkable. Laboratory testing revealed critically low serum cortisol, hypernatremia, and urine studies suggesting diabetes insipidus. The patient was referred to the emergency department. Intravenous fluid resuscitation, corticosteroids, and desmopressin led to significant symptomatic relief. She was maintained on oral hydrocortisone after cosyntropin test revealed adrenal insufficiency. Her clinical picture suggested chronic subclinical adrenal suppression from inhaled corticosteroids, which was exacerbated by hypopituitarism possibly from concussion combined with diabetes insipidus. Adrenal insufficiency should be considered in athletes with history of corticosteroid use and endocrine-related symptoms after concussion, because this can create significant morbidity and can mimic traditional symptoms of concussion.