Pituitary apoplexy presenting as refractory hyponatremia

A previously healthy 24-year-old man presented with subacute worsening headache. Initial evaluation revealed euvolemic hypotonic hyponatremia and central hypothyroidism. Brain magnetic resonance imaging (MRI) demonstrated a sellar lesion concerning for a Rathke cleft cyst vs hemorrhagic macroadenoma. His hyponatremia was initially attributed to syndrome of inappropriate antidiuretic hormone and treated with fluid restriction and hypertonic saline. However, his hyponatremia and neurologic symptoms worsened. Given the patient's headache and sellar pathology, pituitary apoplexy was considered. A pituitary panel was obtained and empiric hormone replacement therapy initiated with IV hydrocortisone (100 mg every 6 hours) and levothyroxine (100 mcg daily). His symptoms and laboratory abnormalities improved to near-complete resolution within 72 hours. Pituitary testing confirmed panhypopituitarism. The patient was discharged on levothyroxine and a hydrocortisone taper. A follow-up pituitary MRI demonstrated interval reduction in lesion size. At 6-month follow-up, recovery of the pituitary axes was observed except for residual GH deficiency. Pituitary apoplexy is a medical emergency requiring prompt recognition and initiation of hormone replacement therapy. Secondary adrenal failure may cause hyponatremia that is refractory to standard therapy, thus mandating its consideration in this setting.