Adrenal incidentaloma diagnosed as pheochromocytoma by serum chromogranin A and plasma metanephrines

Abstract

A 61 year old woman underwent an abdominal ultrasound for heartburn and mild renal insufficiency. A mass of the left adrenal gland was detected. CT and MRT confirmed a left adrenal mass of 2.5×1.7cm size. The patient suffered from stable hypertension without hypertensive attacks or other symptoms suggestive of pheochromocytoma. Under treatment with ramipril, hydrochlorothiazide and prazosin blood pressure was less than 140/90mm Hg. Timolol eye drops were administered for chronic glaucoma. In addition, the patient had diabetes mellitus type 2 with nephropathy and a hiatal hernia. She reported increasing hair-growth at chin and upper lip for about half a year. Except for obesity (height 164cm, weight 111kg), physical examination was otherwise unremarkable. Serum creatinine was 122µmol/l (normal: 45–84), DHEAS 5.32µmol/l (high), FSH 102 U/l (high), E2 29 pmol/l (low), electrolytes were normal. The low-dose (2mg) dexamethasone suppression test, plasma aldosterone/renin ratio, and initial 24h-urinary catecholamine and metanephrine levels were in the normal range. Serum chromogranin A was 517µg/l (normal: <110). A second determination of 24h-urinary catecholamines and metanephrines showed a less than 2-fold increase of metanephrines. Using HPLC, levels of free plasma metanephrine were 3-fold and of normetanephrine 2-fold elevated. An MIBG scan showed increased uptake only in the left adrenal region. Pheochromocytoma was suspected. Left-sided adrenalectomy was performed and pheochromocytoma histologically confirmed. Postoperatively, hypertension and diabetes mellitus improved. This case underscores the superiority of measuring free plasma metanephrines by HPLC for the diagnosis of pheochromocytoma during evaluation of an adrenal incidentaloma. In addition, it demonstrates that measuring serum chromogranin A in combination with urinary fractionated metanephrines can also be useful in this setting, especially in hospitals where HPLC-measured free plasma metanephrines cannot be determined.