Endocrine Abstracts

Introduction: Adrenal medullary hyperplasia (AMH) is a rare, benign disorder marked by overproduction of catecholamines. AMH shares clinical similarities with pheochromocytoma (PCC) but differs in cellular structure and lacks the polygonal cell proliferation typical of PCC. Information on AMH is sparse. We present this case to broaden understanding of AMH’s role in endocrine hypertension.

Clinical Case: A 59-yr-old female with a history of treated hypertension and asthma was referred for investigation of possible carcinoid syndrome. Presenting symptoms included tachycardia, flushing, episodic anxiety, breathlessness and fatigue. On examination, the patient was hypertensive (BP 167/95 mmHg) and tachycardic (HR 127 bpm). Systemic examination was normal. ECG confirmed sinus tachycardia, and echocardiogram showed normal left ventricular function. 24-hour urine 5-HIAA excretion was normal, but plasma normetanephrine was mildly elevated (1510 pmol/l). The clinical history and biochemistry were indicative of PCC. Adrenal CT scan showed slight nodularity within the left adrenal nodule and MIBG SPECT scan confirmed unequivocal avidity in the left adrenal gland, consistent with a left PCC. Laparoscopic left adrenalectomy after adequate preoperative alpha-blockade and tachycardia management with a calcium antagonist (Diltiazem XL) was undertaken after MDT discussion. Histology of the excised adrenal gland showed adrenal medullary hyperplasia rather than classical PCC. Plasma normetanephrine remained elevated (1410 pmol/l) after surgery suggesting possible bilateral adrenal medullary hyperplasia. Genomic analysis was negative for PPGL predisposition genes.

Discussion: AMH is thought to represent a PCC precursor lesion and is more likely to be associated with a genetic condition compared to PCC. Metanephrine levels are reported to be lower in AMH compared to PCC. The presence of elevated metanephrines after adrenal surgery suggests the possibility of bilateral disease. AMH may evolve into classical PCC over time and lifelong follow up is mandatory to monitor hypertension and disease progression.