Adrenal Cortical Atrophy

The adrenals are two crescent-shaped glands that sit on top of each kidney. The adrenal glands secrete hormones directly into the bloodstream. They are divided anatomically and functionally into two main parts: the medulla (middle) and the cortex (rind). Additionally, each division of an adrenal gland consists of internal layers that produce different hormones. Constant stress and poor nutrition can weaken the adrenal glands. When stress continues over prolonged periods of time, the adrenal glands can deplete the body's hormonal and energy reserves, and the glands may either shrink in size or hypertrophy (enlarge).

Adrenal cortical atrophy is the destruction of the outer layer of the adrenal glands. This results in deficient production of hormones called mineralocorticoids and glucocorticoids.

Addison disease or primary adrenocortical deficiency results from destruction of the adrenal cortex. Glucocorticoid, mineralocorticoid and sex steroid production are all reduced.

Signs of Adrenal Cortical Atrophy

The most common signs of this disorder are lethargy, vomiting, loss of appetite, and weakness. Other signs such as diarrhea, weight loss, increased thirst and increased urination may also be evident. The destruction of the adrenal glands is a gradual process. Initially partial destruction of the adrenal cortex produces symptoms that are only obvious during stressful situations such as boarding, travel or surgery. As the adrenal glands are progressively destroyed, the symptoms are evident even in non-stressful situations, and the majority of dogs have chronic problems that may have been present for up to one year. Dogs most at risk are young to middle aged female dogs and castrated male dogs.

Cause of Adrenal Cortical Atrophy

In addition to autoimmunity and tuberculosis, infectious fungal diseases (coccidioidomycosis and histoplasmosis) or viral infections (cytomegalovirus and HIV) have been reported to be responsible for chronic adrenal damage leading to clinical adrenocortical insufficiency (Addison disease). Primary tumors or metastases from malignant tumors elsewhere (lung, breast, stomach, lymphomas, and melanoma) are known to cause chronic adrenal insufficiency.

Adrenal Glands

The adrenal glands secrete mineralocorticoids (primarily aldosterone) to maintain sodium and water balance; glucocorticoids (primarily cortisol) to regulate carbohydrate, fat, and protein metabolism; sex steroids (androgens and estrogen); and catecholamines (mainly epinephrine, norepinephrine, and dopamine) to regulate reactions to stress.

Cytomegalovirus

Cytomegalovirus is a member of the herpesvirus group, which also includes herpes simplex virus types 1 and 2, varicella-zoster virus (the virus that causes chicken pox), and Epstein-Barr virus. This virus can survive in the body in a dormant state for months to years after an individual has been infected. Once infected, an individual retains the living virus within the body for life.

Adrenal cortical atrophy has been reported to result from alpha-particle irradiation to the lymphatic system. If treated, patients with this diseases can have a normal lifespan.