The adrenal glands of dogs with Cushings disease (hyperadrenocortism) produce excessive amounts of hydrocortisone, a hormone with potent anti-inflammatory and immuno-suppressive effects.
There are three basic causes of Cushings disease . These include pituitary-dependent hyperadrenocorticism, adrenocortical cancer, and iatrogenic (medically induced) hyperadrenocorticism.
About 85 percent of dogs with Cushings have an overactive pituitary gland which is a small pea sized gland in the brain producing an excessive secretion of a hormone ACTH. This in turn, overstimulates the adrenal glands to produce hydrocotisone in excess. The majority of the remaining cases result from
adrenal tumours. About 50 percent of the adrenal tumours are benign. Iatrogenic hyperadrenocortism is due to prolonged administration or cortisone. These medications are used to treat a variety of illness in dogs.
Cushings disease is usually seen in middle aged to older dogs, and some breeds, such as Boston terriers, poodles, dachshunds, boxers, Scotties, and German shepherds, seem to be genetically predisposed to it. All breeds, however, can be affected.
The signs of Cushings include hair loss, excessive drinking and urination, exercise intolerance, pot-bellied abdomen, chronic infections, bilateral symmetrical hair loss. But because these signs are not specific to Cushings, vets have to perform several laboratory tests to confirm the disease and then determine its exact cause. Some dogs with Cushings disease will also develop diabetes.
As stated before, most of patients suffer from the pituitary form of Cushings. In such cases, medication can help dogs live out their years in healthy hormonal balance. Trilostane a drug that affects some of the hydrocortisone-producing adrenal cells, is the drug most frequently used to treat this disease.. It works by blocking adrenal gland production and the dog will require monitoring.
The goal is to normalise hormone levels without creating a hydrocortisone deficiency, which would also adversely affect health.
Although standard protocols and doses are used, it is impossible to predict what doses will work for an individual dog. The administration protocol involves an initial loading or induction phase. This involves giving the medication daily until clinical signs resolve. The most common sign used is a decrease in water consumption. Then a maintenance phase is developed that uses a dosage once or twice weekly.
Throughout treatment - and especially during the 5 to 14 day induction phase - owners need to closely watch their dogs for listlessness, loss of appetite, vomiting, and diarrhoea - indications that hydrocortisone levels have fallen too low.
Periodic laboratory tests and dosage adjustments will probably be made during the lifelong treatment of Cushings disease. About 50 percent of dogs treated for the pituitary form of Cushings will relapse at some point.
Other options are available for the treatment of Cushings disease.. One alternative is ketoconazole, an antifungal drug that interrupts hydrocortisone synthesis in the adrenal glands. drug Cushings disease is complex and may be difficult to fathom initially. But most owners discover that treating andmonitoring their dog becomes second nature before long.
NB Treatment for Cushings may provoke the oppposite condition of Addisons
Addisons disease Addisons disease (hypoadrenocorticism) is caused by a lower than normal production of hormones, such as hydrocortisone and aldosterone, by the adrenal glands. The adrenals are small glands that are located near the kidneys. Adrenal hormones are necessary to control salt, sugar and water balance in the body.
Addisons disease occurs less commonly than the opposite condition, Cushing's disease (overproduction of hydrocortisone) in dogs, and is rare in cats.
Addisons disease occurs most commonly in young to middle-aged female dogs. The average age is about 4 years old. The signs of Addisons disease may be severe and appear suddenly, or may occur intermittently and vary in severity. Signs may include weakness, depression, lack of appetite, vomiting, diarrhoea, and occasionally increased thirst (polydipsia) and increased urine production (polyuria).
When a pet is stressed, their adrenal glands produce more hydrocortisone, which helps them deal with the stress. Because dogs with Addisons disease cannot make enough hydrocortisone , they cannot deal with stress, so the signs may occur or worsen when stressed. What a dog finds stressful depends upon his/her temperament. For many dogs, any change in their day-to-day routine, such as being boarded or having house guests, is stressful and may precipitate or worsen signs of Addisons disease.
On examination of dogs with Addisons disease one may see depression, weakness, dehydration, weak pulses and sometimes a slow, irregular heart rate.
Routine laboratory tests often show a low blood sodium and high blood potassium. Loss of water, in vomit and diarrhoea, can lead to dehydration. Severe dehydration increases waste products in the blood (creatinine and blood urea nitrogen = BUN) that are normally eliminated by the kidneys. Addisons disease can be confused with primary kidney disease. Some dogs with Addisons disease have low blood sugar.
Sick dogs often show a pattern of changes in their white blood cells (WBCs) called a stress leukogram. This pattern of changes in the WBCs is caused by hydrocortisone. The absence of a stress leukogram in a sick dog may be a clue to consider Addisons disease. The urine is often dilute.
Increased blood potassium can cause life-threatening abnormalities in the heart rhythm. These abnormalities can cause the heart rate to be slow and irregular and can be seen on an electrocardiogram (ECG).
X-rays of dogs with Addisons disease do not show any specific abnormalities. The heart may appear smaller than normal and rarely the oesophagus (tube from mouth to stomach) can be enlarged.
The history, physical examination, and initial laboratory tests provide suspicion for Addisons disease, but a more specific test, an ACTH challenge, should be performed to confirm the disease . Long-term thot There are two stages of treatment for Addisons disease; in-hospital treatment and long term treatment. Very sick dogs with Addisons disease require intravenous fluids, hydrocortisone-like drugs and drugs to neutralize the effects of potassium on the heart.
Long-term treatment involves the administration of hormones in one of two forms; either a daily tablet or an injection given about every 25 days. Because dogs with Addisons disease cannot produce more hydrocortisone in response to stress, stress should be minimized whenever possible. It may be necessary to increase the amount of hormone given during periods of stress (e.g. boarding, surgery, travel, etc.).
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