PMON49 Checkpoint Inhibitor Induced Hypophysitis with Growth Hormone Deficiency and Implications for the Treatment of ACTH Deficiency

BACKGROUND/PURPOSE: Hypophysitis is a known complication of immune checkpoint inhibitor (ICI) therapies used in the treatment of malignant cancers. In general, central adrenal insufficiency (AI) and hypothyroidism are the most recognized deficiencies following a diagnosis of ICI induced hypophysitis. As a result, other hypothalamic-pituitary axes (HPAs) are either incompletely evaluated or are disregarded from a therapeutic standpoint. Of particular importance is the growth hormone axis which is well established to affect tissue level metabolism of cortisol and cortisone through its effect on 11 beta hydroxysteroid dehydrogenase in target tissues. Our hypothesis is that growth hormone deficiency is also present in ICI induced hypophysitis. METHODS: We queried current and legacy electronic medical records of patients who received ICI for clinical notes mentioning adrenal insufficiency and concern for hypophysitis using the EMERSE tool. Patients with ICI exposure were included if they had 2 of the following 3 criteria; new onset central AI as defined by a low ACTH and cortisol, pituitary imaging suggestive of hypophysitis, or clinical presentation concerning hypophysitis. Patients were excludedfrom the analysis if there was a history of brain irradiation or in whom the diagnosis was not clear due to high dose steroid exposure prior to biochemical evaluation. RESULTS: Twenty-nine patients met inclusion criteria. Out of 29 patients, 16 underwent testing of the growth hormone axis with IGF-1 (11) and/or random growth hormone level (5). Seventeen patients (59%) had biochemical evidence of deficiency of 3 or more HPAs. Twenty-six patients (90%) had biochemical evidence of 2 or more PHAs. Two patients only underwent evaluation of 2 pituitary axes so it is unknown if they indeed suffered from panhypopituitarism. Most patients (28/29) were prescribed hydrocortisone for AI with an average dose of 20 mg per day. CONCLUSIONS: Our findings are suggestive that growth hormone deficiency may be present in ICI induced hypophysitis. This finding holds implications for cortisol replacement therapy for coexisting AI. When one considers the average adrenal cortisol production is 5.7–7.4 mg/m2/day or 9.5–9.9 mg/day, 20 mg of daily cortisol replacementmay be too high in the face of concomitant growth hormone deficiency. Practice changes may include lower doses ofhydrocortisone replacement or adjustment to cortisone acetate which has been shown to have more favorable effectson tissue level metabolic effects. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.