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 (see Neuroendocrine Tissue Tumors) 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.