Dogs : Adrenal Cortical Atrophy

Adrenal cortical atrophy is the destruction of the outer layer of the adrenal glands which results in insufficient production of mineralocorticoid and glucocorticoid hormones. The adrenals are two crescent-shaped glands that sit on top of each kidney and secrete hormones directly into the bloodstream. They are divided anatomically and functionally into two main parts: the medulla (middle) and the cortex (rind). Furthermore, 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 body's hormonal and energy reserves become depleted, and the glands may either shrink in size or enlarge. 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. 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.

Animals most at risk are young to middle aged female and castrated male dogs. The causes are numerous, including autoimmune diseases, tuberculosis, infectious fungal diseases (coccidioidomycosis and histoplasmosis), and viral infections (cytomegalovirus and HIV). 

In addition, primary tumors or metastases from malignant tumors elsewhere (lung, breast, stomach, lymphomas, and melanoma) are known to cause chronic adrenal insufficiency. In rodents, adrenal atrophy may result from chronic exposure to chlorine-based hydrocarbons that are similar in structure to dioxins, highly toxic carcinogens.1