TNF and hereditary pheochromocytoma-paraganglioma: In addition, serum IL-6 (78.8 pg/mL [normal range < 4]) was elevated, while IL-1β (10 pg/mL) and tumor necrosis factor-alpha (TNF-α; 1.17 pg/mL) levels were normal, which led us to diagnose an IL-6-producing pheochromocytoma.