The adrenal medulla, although apparently not essential to life, plays an important role in response to stress or hypoglycemia. It secretes epinephrine and norepinephrine, which increase cardiac output, blood pressure, and blood glucose and decrease GI activity.
Pheochromocytomas Pheochromocytomas in Animals Pheochromocytomas are rare tumors that originate from the adrenal medulla. They have been most commonly reported in dogs, horses, and cattle. Clinical signs associated with pheochromocytomas... read more 
may develop in domestic animals, most often in cattle and dogs. These secrete epinephrine, norepinephrine, or both. Clinical signs are often absent, and tumors may be incidental findings during evaluation for other conditions or at necropsy.
Other adrenal tumors, such as neuroblastomas and ganglioneuromas, may arise in the chromaffin cells of the sympathetic nervous system.
