Uncontrollable high blood pressure is the hallmark of pheochromocytoma, an endocrine tumor that grows in your adrenal glands, two small hormone-producing glands that sit atop your kidneys.
Pheochromocytoma stimulates the release of excess catecholamines -- hormones including dopamine, adrenaline, metanephrine and noradrenaline the body uses to manage your heart rate, blood pressure, blood sugar and its response to stress. When your body feels stressed, it floods your bloodstream with catecholamines (fight or flight, remember?). When it's a tumor triggering the release of those hormones rather than your body's natural stress response, it can cause chronic, uncontrollable hypertension, headaches, heart palpitations and excessive sweating. It can also cause anxiety, nervousness, paleness, nausea, weight loss, chest or abdominal pain, fatigue and weakness [source: Cleveland Clinic].
Most pheochromocytomas are in the adrenal glands -- more than 90 percent -- and as many as 98 percent are within the abdomen [source: Blake]. When a pheochromocytoma grows outside the adrenal glands it's called a paraganglioma. Paragangliomas often grow in the head and neck, chest, abdomen, or pelvis [source: Pheo-Para Alliance].