Pheochromocytomas are tumors of the adrenal gland that produce excess adrenaline. Pheochromocytomas arise from the central portion of the adrenal gland, which is called the adrenal medulla. The adrenal medulla is responsible for the normal production of adrenaline, which our body requires to help maintain blood pressure and to help cope with stressful situations. A tumor that arises from the adrenal medulla and overproduces adrenaline can be a deadly tumor because of the severe elevation in blood pressure it causes.