SUN-408 Hypercalcemia: A Marker of Glucocorticoid Under replacement and noncompliance in Primary Adrenal Insufficiency

Abstract Disclosure: R. Purbey: None. J.G. Daily: None. Primary adrenal insufficiency (PAI),also known as Addison’s disease,is a rare long-term endocrine disorder affecting around 9-14/100000 people in the developed world.It is characterized by the inadequate production of cortisol and mineralocorticoids leading to electrolyte abnormalities including hyponatremia and hyperkalemia. One of the possible complications of PAI is hypercalcemia which is noted in around 5-6 % of patients at the time of diagnosis.Monitoring adequacy of steroid replacement therapy in PAI is mostly based on signs and symptoms.We present a rare case of PAI where elevated calcium levels served as a marker of nonadherence with glucocorticoid (GC) replacement. Our patient is a 20 y/o male with past medical history of autoimmune polyglandular syndrome with PAI and hypothyroidism;who presented for regular follow-up.He was on GC and thyroid hormone replacement.He had a recent fall which resulted in left clavicle fracture.Clinical examination was unremarkable.Labs showed mildly elevated calcium of 10.1 mg/dL(8.6-10),elevated creatinine at 1.2 mg/dL(0.67-1.17) and elevated phosphorus of 4.7 mg/dL(2.5-4.5).He reported compliance with current treatment regimen.On follow-up after 1 month, labs showed persistent elevation in calcium, creatinine and phosphorus levels at 10.2 mg/dL,1.2 mg/dL and 5.3 mg/dL respectively.Patient's mother reported that patient was missing some doses of his hydrocortisone. After counseling, he resumed recommended treatment regimen. Labs were repeated after 1 month and they revealed normalization of calcium ,creatinine and phosphorus levels at 9.1 mg/dL, 1 mg/dL and 4.4 mg/dL respectively.Patients with PAI on GC replacement therapy are regularly monitored for over-replacement or under-replacement based on symptoms and signs including postural hypotension,energy levels, weakness,dizziness and cushingoid features.Our patient was under replaced and he only had lab abnormalities with consistently elevated calcium levels. Hypercalcemia in PAI is postulated to be due to various causes including increased resorption from bone and decrease removal by the kidneys.On resumption of treatment, his calcium levels normalized.His fall could possibly have been due to dizziness resulting from under replacement.There have been numerous case reports of Addison's disease and adrenal crisis initially presenting with hypercalcemia.This case is one of the rare instances where under replacement of GC therapy in PAI was diagnosed on the basis of elevated calcium levels, and not on the basis of signs and symptoms.The implications of nonadherence with therapy in PAI is adrenal crisis which has a high mortality rate.Our case report therefore demonstrates that hypercalcemia can serve as a marker of noncompliance with therapy in PAI and identifying this can help us in increasing compliance and adherence; thereby reducing the incidence of adrenal crisis. Presentation: Sunday, July 13, 2025