SUN-501 - Pheochromocytoma in Disguise: A Rare Case of Triple Hormone Secretion

Background:

Adrenal incidentalomas may present with heterogeneous and overlapping biochemical abnormalities, complicating diagnosis and management. Primary hyperaldosteronism, mild autonomous cortisol secretion (MACS), and pheochromocytoma are generally considered distinct functional entities arising from the adrenal cortex or medulla. Although rare cases of dual cortical–medullary hormone excess have been reported, to our knowledge, the coexistence of all three syndromes—primary hyperaldosteronism, autonomous cortisol secretion, and pheochromocytoma—has not been previously described.

Case Description:

A 76-year-old female with a 20-year history of hypertension was referred for evaluation of a left adrenal incidentaloma measuring 1.6 cm identified in 2022. Biochemical evaluation confirmed primary hyperaldosteronism with suppressed renin, spontaneous hypokalemia, and elevated aldosterone. Concurrent testing demonstrated MACS, with repeatedly nonsuppressed 1-mg dexamethasone suppression tests and intermittent abnormal late-night salivary cortisol, with a normal 24-hour urine free cortisol. Plasma metanephrine levels were persistently but mildly elevated with DOTATATE imaging showing no evidence of pheochromocytoma.

Given controlled blood pressure and absence of overt Cushingoid features, the patient initially elected medical management and surveillance. Over time, she developed worsening hypertension requiring increased doses of her three antihypertensive agents. Adrenal venous sampling was performed and was inconclusive. She then developed new-onset prediabetes, osteopenia, and biochemical progression of cortisol hypersecretion, including elevated 24-hour urine free cortisol. Based on progressive cardiometabolic sequelae consistent with MACS, she underwent an elective laparoscopic left adrenalectomy in November 2025.

Unexpectedly, surgical pathology revealed a 2.5-cm pheochromocytoma confined to the adrenal gland with negative margins. Postoperatively, she had a normal cosyntropin stimulation test without need for glucocorticoid replacement. Her plasma metanephrines normalized, aldosterone–renin indices improved, and blood pressure control improved with de-escalation of antihypertensive therapy.

Discussion:

This case highlights an exceptionally rare presentation of pheochromocytoma masquerading as adrenal cortical hormone excess. Mild catecholamine elevations and negative functional imaging does not exclude the presence of pheochromocytoma. Progressive cardiometabolic complications in patients with MACS should prompt reconsideration of surgical intervention even in the absence of classic adrenergic or Cushingoid features.

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