Hyperadrenocorticism (Cushing's Syndrome) |
Named after Harvey Cushing, the physician who described the disease in humans in 1932, this is a disorder in which the adrenal glands produce excessive amounts of the hormone cortisol. The adrenals are located on the top of each kidney and their production of cortisol is regulated by adrenocorticotrophic hormone (ACTH) produced by the pituitary gland at the base of the brain.
Cortisol is an important hormone and is one which rises in response to stress. Short term increases may be beneficial but to have the blood levels permanently raised will eventually cause great harm to the body. It is the body's own glucocorticoid and in addition to its role in stress is involved in protein, fat and carbohydrate metabolism.
Cushing's is a disease which can present with many different signs/symptoms, not all of which will be present in every case and many of which could also be suggestive of other illnesses.
Some of the commoner signs include:
As Cushing's tends to affect mainly middle aged and older dogs and as it is often insidious in onset many of the signs may be attributed by the owner to old age and the disease may be quite advanced before veterinary advice is sought. It is commoner in small breeds and there are suspicions that there may be a genetic predisposition to the condition.
Diagnosis
Routine blood biochemistry will not confirm a diagnosis of Cushing's Syndrome although there may be signs such as high cholesterol levels and an increase in liver enzymes which are suggestive of it. A combination of these plus the clinical signs may lead to your vet suggesting more specific blood tests such as an ACTH stimulation test and/or a low dose dexamethasone suppression test.
A positive result to these tests confirms the diagnosis and the low dose dexamethasone suppression test will also indicate whether the disease is of pituitary or primary adrenal origin. In both categories the underlying issue is a tumour, usually benign, which is actively secreting hormones. In small breeds at least 85% of cases are due to a pituitary tumour. In the UK very few cases will be treated surgically, almost all will be managed by drug therapy.
Currently the only drug licensed in the UK for treatment of the disease is Trilostane, marketed as Vetoryl. Trilostane is available in several different strengths and appears to be considerably safer and to give much better results than its predecessors. Unfortunately, like most hormone preparations, it is quite expensive and treatment will be for the duration of the dog's life.
Response to treatment is measured both by improvement in the clinical signs and by follow up blood tests to measure cortisol levels. The tests used are either an ACTH stimulation test or the more recently developed Pre Pill Cortisol test. Testing is usually done 10 days and again 4 weeks and 12 weeks after the start of treatment or after any alteration in the drug dosage. Long term monitoring of stable patients is carried out roughly every 3 months.
Patients with controlled Cushing's enjoy a good quality of life and may do so for a number of years. Often they die from old age rather than the hyperadrenalcorticism. However, it should be noted that affected animals may be more prone to developing other conditions such as hypothyroidism and diabetes. There are also suggestions that they may be at a greatly increased risk of developing Gallbladder Mucocoele.
Cortisol is an important hormone and is one which rises in response to stress. Short term increases may be beneficial but to have the blood levels permanently raised will eventually cause great harm to the body. It is the body's own glucocorticoid and in addition to its role in stress is involved in protein, fat and carbohydrate metabolism.
Cushing's is a disease which can present with many different signs/symptoms, not all of which will be present in every case and many of which could also be suggestive of other illnesses.
Some of the commoner signs include:
- Thirst and excessive urination.
- Tendency to develop urinary tract infections.
- Loss of muscle tone and the development of a "pot-bellied" appearance.
- Thinning of the skin and loss of coat especially on the flanks and tail. This may show as e.g. failure of the coat to regrow after stripping. Sometimes, little nodules of calcium may be laid down within the skin-calcinosis cutis.
- Lethargy and reluctance to exercise.
- Ravenous appetite.
- Panting and breathlessness, particularly at night.
- Bitches may stop coming into season and males may lose their libido and their testes may shrink.
As Cushing's tends to affect mainly middle aged and older dogs and as it is often insidious in onset many of the signs may be attributed by the owner to old age and the disease may be quite advanced before veterinary advice is sought. It is commoner in small breeds and there are suspicions that there may be a genetic predisposition to the condition.
Diagnosis
Routine blood biochemistry will not confirm a diagnosis of Cushing's Syndrome although there may be signs such as high cholesterol levels and an increase in liver enzymes which are suggestive of it. A combination of these plus the clinical signs may lead to your vet suggesting more specific blood tests such as an ACTH stimulation test and/or a low dose dexamethasone suppression test.
A positive result to these tests confirms the diagnosis and the low dose dexamethasone suppression test will also indicate whether the disease is of pituitary or primary adrenal origin. In both categories the underlying issue is a tumour, usually benign, which is actively secreting hormones. In small breeds at least 85% of cases are due to a pituitary tumour. In the UK very few cases will be treated surgically, almost all will be managed by drug therapy.
Currently the only drug licensed in the UK for treatment of the disease is Trilostane, marketed as Vetoryl. Trilostane is available in several different strengths and appears to be considerably safer and to give much better results than its predecessors. Unfortunately, like most hormone preparations, it is quite expensive and treatment will be for the duration of the dog's life.
Response to treatment is measured both by improvement in the clinical signs and by follow up blood tests to measure cortisol levels. The tests used are either an ACTH stimulation test or the more recently developed Pre Pill Cortisol test. Testing is usually done 10 days and again 4 weeks and 12 weeks after the start of treatment or after any alteration in the drug dosage. Long term monitoring of stable patients is carried out roughly every 3 months.
Patients with controlled Cushing's enjoy a good quality of life and may do so for a number of years. Often they die from old age rather than the hyperadrenalcorticism. However, it should be noted that affected animals may be more prone to developing other conditions such as hypothyroidism and diabetes. There are also suggestions that they may be at a greatly increased risk of developing Gallbladder Mucocoele.