Merck Manual

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Professional Version

Adrenal Medulla


David Bruyette

, DVM, DACVIM, Anivive Lifesciences, Inc.

Reviewed/Revised Apr 2019 | Modified Oct 2022

The adrenal medulla is the central portion of the gland and is the primary source of the hormones epinephrine and norepinephrine. With the exception of pheochromocytomas associated with an excess of catecholamines, clinical disease associated with isolated adrenal medullary disease is very rare. Even in animals with primary hypoadrenocorticism, adrenal medullary function appears to be normal, likely due to extra-medullary secretion of catecholamines.

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 Pheochromocytomas in Animals 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.

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