Hypoadrenocorticism - Addison's disease in dogs.

Hypoadrenocorticism - Addison's disease in dogs.
Affected Animals: Dogs. Females are most often affected. Young dogs, between four and five years old, are usually more affected than older dogs. Any breed can be affected, although some studies show that most dogs with Addison's disease are mixed breeds. Veterinarians have also observed a high incidence of diagnosed cases among white West Highland Terriers.
Overview: Known scientifically as canine hypoadrenocorticism, Addison's disease is the result of decreased production of steroid hormones by the adrenal glands. The symptoms of Addison's disease are not very specific and may include lethargy, weakness, gastrointestinal disturbances, and lack of appetite. Often these symptoms appear intermittently over a long period of time.
Although some dogs are diagnosed while in a relatively stable condition, most are not seen until Addison's crisis develops - a severe stage of the disease, when shock and collapse can occur. However, if a dog is treated and successfully removed from a crisis, the long-term prospects are excellent, as most animals can be treated with oral or injectable medication to replenish the deficient hormones.
Clinical Signs: Clinical signs include anorexia, or absence of appetite, weight loss, depression, vomiting, diarrhea, weakness, collapse, polyuria or excessive thirst, signs that appear and disappear temporarily, shaking and jerking, and abdominal pain.
Description: Addison's Disease is a syndrome that results from the inability of the adrenal glands to produce normal hormones. The adrenal glands are two small structures, located on top of each kidney. Most of the hormones that they produce are steroids. These steroids fall into two main groups: mineralocorticoids and glucocorticoids. Aldosterone, the main hormone of the mineralocorticoid group, plays a major role in the regulation of sodium and potassium and in water balance.
Cortisol, the main hormone of the glucocorticoid group, acts in almost all tissues of the body, helping to regulate glucose production, and in metabolism, influencing the solubilization of fat and protein, stimulating the formation of red blood cells in the blood and helping to balance blood pressure, neutralizing stress, and suppressing inflammation.
Despite their different control mechanisms, both groups of steroids are generally affected by primary adrenal gland insufficiency in Addison's Disease. Some animals will exhibit symptoms primarily associated with mineralocorticoid deficiency, while others will have problems with glucocorticoid deficiency. Although sex hormones such as estrogens and androgens are also produced by the adrenal glands, symptoms due to deficiency of these hormones do not occur in dogs with Addison's Disease.
The destruction of 85 to 90 percent of the steroid-producing cells in the adrenal glands appears to be necessary for secondary signs of mineralocorticoid and glucocorticoid deficiencies to develop. This destruction is most commonly due to destruction of the adrenal glands by problems in the immune system. Less frequently, infections, inflammation, cancer, medications, or abnormalities of the blood supply to the adrenal gland may contribute to the development of Addison's Disease.
Secondary adrenal gland insufficiency can also occur, due to problems affecting the hypothalamus or pituitary gland, resulting in symptoms of Addison's Disease. Addison's Disease symptoms may follow an intermittent course, often appearing and disappearing, over a long period of time, before the disease is suspected.
Occasionally, Addison's Disease can be diagnosed in dogs with relatively mild symptoms. It is common, however, that the diagnosis is only made when a very severe attack appears as a result of the disease. These crises are characterized by severe symptoms, followed by shock and collapse.
Prognosis: With appropriate medical treatment, the long-term prospects for dogs with Addison's Disease are excellent. Effective communication between owner and veterinarian is vital to the management of dogs with Addison's Disease and owners should keep a supply of prednisone on hand for crisis situations.
Treatment: The treatment of dogs with Addison's Disease depends on the severity of the signs presented. Many animals with the disease are gravely ill, sometimes life-threatening, due to fluid deficits and abnormal electrolyte concentrations. These animals should receive immediate medical attention, as prompt care is extremely important to stabilize dogs in Addison's crisis.
Prevention: There are no means of prevention.