Abstract
Adrenal insufficiency is a known complication of both immune checkpoint inhibitors (ICIs) and resection or ablation of the adrenal glands. In the modern era of immunotherapy, more frequent assessment of the adrenal hormonal axis is performed after initiation of ICIs in order to monitor for such complications. The interpretation of these laboratory tests, such as elevated adrenocorticotropic hormone (ACTH), in patients who receive ICIs and undergo adrenalectomy or adrenal ablation provides an additional set of diagnostic challenges that are not well described. We present a case series of four patients who had elevated ACTH without clinical (symptoms) or biochemical (decreased cortisol) evidence of adrenal insufficiency, a pattern suggesting a compensatory increase in ACTH. This highlights an emerging phenomenon and diagnostic challenge in the monitoring of the adrenal axis in patients undergoing adrenalectomy or ablation alongside ICI therapy, emphasizing the need for close follow-up and thorough investigation to rule out adrenal insufficiency in such patients.