Abstract

Fever is one of the most common symptoms observed in infectious diseases. However, non-infectious causes should also be considered in the differential diagnosis. In patients presenting with a common symptom such as fever, it is important to keep adrenal insufficiency in mind as a rare but possible underlying cause. A 54-year-old woman with a history of coronary artery disease, hypertension, and hypothyroidism presented with complaints of fatigue, weakness, nausea, vomiting, abdominal pain, headache, and fever. Her past medical history was notable for a previous pituitary adenoma surgery. Laboratory tests revealed elevated C-reactive protein (65 mg/L) and procalcitonin levels (33.2 ng/mL). To investigate a possible infectious etiology, neck, thoracic, and abdominal computed tomography, transthoracic echocardiography, blood and urine cultures, and other infectious disease workups were performed, but no pathology was identified. Pituitary magnetic resonance imaging revealed a macroadenoma. Laboratory findings showed hyponatremia and decreased early morning cortisol levels (1.82 μg/dL), while adrenocorticotropic hormone (ACTH) levels were within the normal range. A high-dose ACTH stimulation test confirmed the diagnosis of secondary adrenal insufficiency. The patient showed a dramatic clinical improvement after glucocorticoid replacement therapy and was discharged with an appropriate treatment plan. When investigating the cause of fever, a thorough medical history, repeated physical examinations, and appropriate use of laboratory and imaging studies are essential. Common etiologies should be considered first, and if no diagnosis is established, rare causes must be carefully evaluated.