SHM Converge Scientific Abstract ePoster Gallery-Pembrolizumab-Induced Secondary Adrenal Insufficiency in a Patient With Triple Negative Breast Cancer

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This case report describes pembrolizumab-induced secondary adrenal insufficiency in a 75-year-old woman with stage IIB triple negative breast cancer receiving adjuvant radiation and cycle 3 of pembrolizumab. She presented with fatigue and myalgia and was found to have worsening hyponatremia. Initially, her low sodium was treated as possible hypovolemic hyponatremia with IV normal saline and later salt tablets, but her sodium continued to fall after these were stopped.<br /><br />Further evaluation on hospital day 3 showed an inappropriately concentrated urine, low serum cortisol (3.3 mcg/dL), and an abnormal ACTH stimulation test, with ACTH in the low-normal range, consistent with central adrenal insufficiency. The diagnosis was pembrolizumab-induced hypophysitis causing secondary adrenal insufficiency. She was started on hydrocortisone 40 mg twice daily, after which her sodium gradually improved and her symptoms resolved. She was discharged on day 5 with sodium normalized to 132 mmol/L.<br /><br />The report highlights that immune checkpoint inhibitors such as pembrolizumab can cause rare but serious endocrine immune-related adverse events, including hypophysitis and adrenal insufficiency. Clinicians should consider adrenal insufficiency in patients on ICIs who develop fatigue, hyponatremia, hypotension, hypoglycemia, or hyperkalemia. The authors emphasize that euvolemic hyponatremia may be misdiagnosed as hypovolemia at first, and repeating urine studies after saline administration can help distinguish causes. Early recognition and prompt steroid replacement are critical to prevent life-threatening complications.

Asset Subtitle

Liz J. Thaliath

Meta Tag

Author List Joseph Edmund, Liz J. Thaliath, Sowjanya Bapani

Category Clinical Vignettes

Concept Pembrolizumab

Concept Secondary Adrenal Insufficiency

Concept Glucocorticoid Replacement

Concept Immune Checkpoint Inhibitor

Concept Hypophysitis

Distinguished Non-Finalist

Presenter Organization Marshfield Clinic

Presenting Author Liz J. Thaliath

Track Adult

Keywords

pembrolizumab

secondary adrenal insufficiency

hypophysitis

hyponatremia

immune checkpoint inhibitor

triple negative breast cancer

hydrocortisone

ACTH stimulation test

endocrine adverse event

euvolemic hyponatremia

Pembrolizumab

Secondary Adrenal Insufficiency

Glucocorticoid Replacement

Immune Checkpoint Inhibitor

Hypophysitis