What is cushing’s syndrome?
Most species of animals have naturally occurring cortisone in their bodies. A small pair of glands located near each kidney called the Adrenal Glands produces the cortisone, under guidance from the pituitary gland in the brain. An excess of cortisone in the system is known as Cushing’s Syndrome. Cortisone is essential for life, at balanced quantities. A deficiency of cortisone is known as Addison’s Disease.
What causes too much cortisone in the body?
Cushing’s syndrome can occur naturally or as a temporary side effect of your pet receiving cortisone mediaction but will resolve once medication is withdrawn. In naturally occurring Cushing’s disease a minority of the dogs will have a tumour in one of the two adrenal glands (mostly in large breed dogs). The majority have a small tumour at the base of the brain in an area called the pituitary gland. The pituitary gland controls the adrenal function. A tumour in the pituitary causes excess production of cortisone and results in the symptoms we see as Cushing’s disease.
What are the symptoms of cushings?
When Cushing’s Disease occurs it may have varying symptoms. Not all dogs present with the same symptoms, but most have at least two or three of the more commonly observed abnormalities.
- Excess urination and increased water consumption: dogs may urinate for longer time periods or they urinate more frequently. There may also be leakage of urine during sleep. The increased urination is accompanied by increased thirst.
- Voracious appetite: the increase in cortisone causes the dog to be hungrier than normal. Monitoring the appetite is important in the treatment of the condition.
- Loss of hair with no re-growth: Hair loss is most commonly observed along the back, sides, abdomen and tail and on the backs of the hind legs. The coat may become thin or there could be a complete hair loss resulting in patches of baldness. The coat may not regrow after clipping. Some dogs develop a dull, harsh coat. The feet and head is almost never affected.
- Muscle weakness and lethargy: Dogs with Cushing’s disease may have difficulty jumping, climbing stairs, and rising after they have been sitting or lying down or tiredness after going on walks. The muscle weakness can also result in the “pot-bellied” appearance quite commonly seen.
- Thinning of the skin and skin infections
- Panting, especially at night. Dogs may also seek out cool areas toe lie, like tile floors.
- Increased liver size on abdominal palpation
Testing for cushings
Examining the dog’s symptoms and obtaining a thorough history guides us to the diagnosis. Screening blood tests are required, typically revealing elevated red cell and possibly bood platelet counts, white blood cell changes consistent with a so-called “stress leucogram”, elevated ALP (a liver enzyme) and possibly elevated blood glucose levels. Specific blood tests are required to confirm the diagnosis. We generally prefer the ACTH stimulation test in the majority of patients. Occasionally, the “Low Dose Dexamethasone Suppression Test” may be done, but this test can be susceptible to external or other disease influence and we perform the test only in exceptional cases. The urine cortisol ratio test can help to rule out Cushing’s disease. The ACTH stimulation test requires about 1 hour to perform the two required blood samples and then another hour to perform the blood tests in our in-house laboratory. An ultrasound examination is usually also performed to visualise the adrenal glands and help distinguish adrenal gland tumours from pituitary tumours in most cases.
Treatment of cushings
Treatment of this condition is vital to help restore a good quality of life to your dog. Most patients treat very successfully, but there may be complications. Pituitary dependent Cushing’s disease generally responds more predicatably to treatment, but even large and metastatic adrenal gland tumours can respond favourably.
At the CAMC we treat Cushing’s disease with a medication called Lysodren. Following diagnosis of the condition the patient is put onto an initial twice daily induction dose. This is continued for no more than 10 days. Each dose will destroy a small part of the function of the adrenal gland, decreasing the cortisone excreted. The key to treatment is to note your dog’s appetite and to stop the induction dose as soon as you notice any decrease in the appetite or drinking. Reduction in appetite may be noted as the dog taking longer to finish a meal, eating less than normal, wandering away and then returning to finish, or pausing to look up at the owner during meals. As soon as ANY decrease in appetite or drinking is seen please stop the induction dose of medication, and contact us to repeat the ACTH stimulation test. If this is over a weekend, the test can be done on the Monday. If the blood results are satisfactory (the adrenal glands are adequately suppressed) your dog will be placed onto a maintenance dose of the Lysodren medication for life usually involving taking the Lysodren twice per week. Too long or excessive treatment may result in a deficiency of cortisone which will then need to be treated by supplying cortisone. Careful owner observation is therefor critical.
In South Africa there is no registered medication freely available for treatment of Cushing’s disease. Luckily we can obtain Lysodren after obtaining a licence from the Medicine Control Council. We will need to see your dog on a regular basis to monitor its progress. Due to the regulations involved regarding unregistered medications we need to see your dog at least once every 6 months once adequate control of your dog’s condition has been obtained so that we can report back to the Medicine Control Council. This is an administrtative task we take care of.
Most dogs with Cushings disease treat very successfully, and often for very long periods of time (years in many cases). Succesful treatment far exceeds treatment failures. However, complications may include stroke, enlargement of the pituiray gland resulting in compression of the brain, diabetes and spread (metastasis) of adrenal tumours.