A Case of a Multitasking Adenoma: Primary Aldosteronism and Subclinical Cushing Syndrome

Introduction: Post-operative adrenal insufficiency is an uncommon complication after unilateral adrenalectomy for an aldosterone producing adenoma. However, clinically significant post-operative adrenal insufficiency is rare and understudied. Here we present a case of subclinical Cushing’s syndrome (SCS) resulting in postoperative adrenal insufficiency. Case Description: A 39-year-old female followed with nephrology for chronic kidney disease due to polycystic kidney disease and hypertension. She developed increasing blood pressure over approximately two months. Laboratory evaluation identified hypokalemia. A secondary hypertension work-up showed aldosterone/renin activity ratio was 592. Imaging identified a left adrenal adenoma with adrenal vein sampling consistent with left adrenal gland aldosterone hypersecretion. Prior to surgery, a dexamethasone suppression test was completed with a serum cortisol of 2.6 mcg/dL (reference range <1.8 mcg/dL) consistent with SCS. She underwent left adrenalectomy, and due to her SCS, was initiated on maintenance hydrocortisone for possible post-operative adrenal insufficiency. Three weeks after hospital discharge, she developed nausea and fatigue. Laboratory evaluation demonstrated a cortisol level of 4.8, sodium level of 120, potassium level of 4.6, aldosterone level of 14, and ACTH level of 15.8. She reported discontinuation of hydrocortisone a week earlier. She resumed hydrocortisone and hyponatremia resolved, and potassium level has remained within the standard range. Discussion: The incidence of adrenal insufficiency post unilateral adrenalectomy for non-cortisol secreting tumors is estimated to range between 27% to 34%. Primary aldosteronism plus SCS is estimated to range between 10% and 20% based on recent cohort studies, where postoperative adrenal insufficiency is reported to be around 65%. A standardized protocol has not been developed to screen for primary aldosteronism plus SCS. Screening for SCS prior to unilateral adrenalectomy can be an effective way to identify a population with increased risk for clinically significant postoperative adrenal insufficiency.