What happened, in summary

A 65-year-old woman with recently diagnosed metastatic lung adenocarcinoma had a left cerebellar metastasis that was surgically removed. She was receiving nivolumab immunotherapy when she developed five days of nausea, vomiting, and diarrhea, together with a week of fatigue, malaise, and headache. On admission, her blood pressure was low, and she became increasingly confused over the next two days.

Imaging showed the known right upper-lobe lung mass and postoperative changes from the cerebellar surgery. Brain MRI found no residual mass and no pituitary lesion. Laboratory testing showed low cortisol with high adrenocorticotropic hormone and an inadequate cortisol rise after stimulation testing. Low aldosterone, high renin, and hyponatremia supported primary adrenal insufficiency caused by nivolumab-related adrenalitis rather than pituitary inflammation.

She received intravenous fluids and hydrocortisone 100 mg every eight hours, later tapered to 60 mg every 12 hours. Fludrocortisone 0.2 mg daily was also started to replace mineralocorticoid function. Her symptoms improved, and her sodium level returned to 136 mEq/L.

She was discharged on hydrocortisone 30 mg daily and fludrocortisone 0.1 mg daily. The report documents recovery from the endocrine complication but does not establish the latest status of the metastatic lung cancer. Her experience highlights how a serious immune-related hormone deficiency can emerge during immunotherapy and require long-term replacement treatment.