Addison's Disease

ENDOCRINE SYSTEM

Endocrine Organs:

Include the pancreas, thyroid gland, parathyroid glands and adrenal glands. Diseases of the endocrine system may lead to the production of too much or too little hormone.

kidney and adrenal glands

Adrenal Glands:

The adrenal glands are in close proximity to the kidneys. The outer portion of the adrenal glands are located on top of each kidney, this is called the adrenal cortex.

The adrenal cortex produces, among other things, steroid hormones which regulate carbohydrate and fat.

Addison’s Disease:

Addison’s disease is the common name for Hypoadrenocorticism* and this disease can occur in dogs of any age, sex or breed although more females are affected than males. It usually is a disease of young and middle aged dogs. The disease is a ‘great mimic’ and can be very difficult to diagnose as there is no one clinical sign specific to Addison’s and these may resemble signs of other illnesses.

The adrenal gland can be damaged by approximately 90% before signs of the disease are seen. The hormones produced by the adrenal glands are important for life. This disease, once diagnosed, can be treated by replacing the hormones produced by the glands which are required for survival.

The adrenal glands secrete adrenal hormones which modify the body’s response to inflammation, stimulate the liver to raise the blood sugar, and also help to control the amount of water and salt in the body which affects blood volume and blood pressure. Addison’s disease is a severe or total deficiency of the adrenal hormones.

Adrenal insufficiency can be primary or secondary. Primary adrenocorticism affects the salt/potassium balance in the body and glucocorticoid as well. Secondary adrenocorticism usually affects glucocorticoids. It is not known why primary adrenocorticism occurs but it is thought it might be an immune mediated process.

Secondary adrenocorticism probably occurs most often when prednisone or other cortisones being administered for medical reasons are suddenly withdrawn. It can occur if, for example, pituitary cancer interferes with the production of hormones that stimulate the adrenal glands.

Signs can be vague; more severe signs occur when a dog with hypoadrenocorticism is stressed or when potassium levels get high enough to interfere with heart function.

Dogs will sometimes suffer severe shock symptoms when stressed which can lead to rapid death. When potassium reaches high levels heart stoppage can occur which can be fatal. In some cases, particularly regarding secondary Addison’s disease, there are no detectable electrolyte changes.

*(Cushings disease is the common name for Hyperadrenocorticism)

Signs & Symptoms:

The clinical signs are variable

  • Initially the signs may be mild and very vague.
  • With an acute crisis the signs are more pronounced.
  • Lethargy & weakness
  • Poor appetite
  • Vomiting
  • Diarrhoea
  • Weight loss
  • Depression
  • Dehydration
  • Excessive thirst and water intake (polydipsia)
  • Low body temperature, shaking, collapse, low heart rate
  • Please refer to the Comparison Chart of Hereditable Diseases for signs and symptoms of this disease.

It is not known if Addison’s disease is an inherited disease in the Wheaten Terrier, although there appears to be a higher than average predisposition for it.

Diagnosis:

This disease can be hard to differentiate from renal failure as the symptoms and even the blood work can be similar. Electrolyte levels can show as normal but Addison’s can sometimes be diagnosed by picking up the changes in the ratio between sodium and potassium levels, this can be easily missed unless it is specifically looked for.


ACTH Response Test

The ACTH response test will be necessary to make an accurate diagnosis.

Dogs are usually admitted to the vet’s surgery for a couple of hours. Blood is taken for analysis, followed by an injection which stimulates the production of adrenal hormones. After approximately 1½ -2 hours blood is again taken for analysis, if the production of the adrenal hormones is negative then Addison’s disease (hypoadrenocorticism) is diagnosed.


Treatment:

This depends on whether the onset of illness is acute with severe symptoms, or whether more mild chronic signs are present.

For acute signs, i.e. Addisonian crisis, treatment would be administered by emergency admittance to the vet’s surgery. This may include intravenous fluid therapy, electrolyte and acid-base monitoring, and corticosteroid and mineralocorticoid replacement therapy.

For chronic disease it may include corticosteroid and mineralocorticoid replacement therapy and daily salt supplementation. Hopefully, the disease will be diagnosed before an Addisonian crisis occurs and treated with prescribed medications.

At home the dog needs a stress reduced environment since its glands cannot produce the hormone that helps it handle stress. Stress can cause relapses of symptoms if not properly treated.

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