Your dog or cat has 2 adrenal glands. Although the name and the placement in the body suggest otherwise, the adrenal glands have a completely different function to the kidneys. The adrenal glands consists of the adrenal cortex and medulla. The cortex produces steroid hormones (cortisol, aldosteron and androgens) and the medulla produces adrenaline and noradrenaline. With Cushing's syndrome the adrenal glands do not work insufficiently, on the contrary, they produce too much cortisol.
Causes for Cushing's Sydrome
Cushing’s syndrome is most common in dogs, it is rarely seen in cats. Dr. Cushing, a US neuro-surgeon (1869-1939) was the first one to describe the disease. With Cusing’s syndrome too much cortisol is produced by the adrenal glands. A tumor of the adrenal cortex can be the cause, but in most cases (90%), the tumor is being caused by a benign tumor of the pituitary gland (protrusion off the bottom of the hypothalamus of the brain).
The pituitary gland produces several hormones that in their turn stimulate subservient glands like the adrenal glands. One of these hormones is ACTH (AdrenoCorticoTropic Hormone ) which gives the adrenal glands the "order" to produce more cortisol.
With so called iatrogenic Cushing’s syndrome there is another cause. (iatrogenic means caused by medical treatment)
With this type of Cushing’s it is not your dog or cat’s body that produces too much cortisol, but it is a reaction of the body to a too high amount of cortisol that is externally supplied in the form of tablets or injections. Cortisone is the inactive form of cortisol, the latter being produced inside the body.
These medicines are often prescribed with e.g. asthma or arthritis. How much cortisones over what period of time result in the development of Cushing’s syndrome in a dog or cat can differ per animal. Some animals are treated with cortisones for years without any problems, other animals develop symptoms after a very short time.
When your pet develops iatrogenic Cushing's syndrome, stopping the cortisone treatment is the best therapy. But you must never stop giving the cortisone tablets all at once, that can be life-threatening for your pet because the adrenal glands have become "lazy" from the cortisol supplied through the medication and they are producing very little cortisol themselves. The treatment with cortisone should be ended really slowly under supervision of your vet and if it not possible to end the treatment completely it should be reduced as much as possible, otherwise a life-threatening Addisonian crisis ( adrenal insufficiency) can occur.
Symptoms in the early stages of Cushing’s syndrome.
Because there is too much cortisol in the body, a number of symptoms can develop. At first you probably notice that your pet eats a lot more, is very thirsty and has to urinate more often. The coat grows more slowly or bald spots occur. The colour can also change, e.g turn lighter. The skin can become thin and folded, wounds heal more slowly and blue spots can occur. Your pet tires more easily. Moreover, the skin is prone to infections by e.g bacteria and fungi, because too much cortisone decreases the natural resistance of the body.
Other symptoms Cushing’s syndrome.
There are also other serious illnesses that can develop in your dog, such as osteoporoses. (decalcification of the bone) This occurs because the body breaks down protein more rapidly because of the cortisone, causing the bones to fracture more easily. Muscle tone also decreases, they get more flaccid and at the same time there is more fat deposition over the rump: your pet has thin legs and a fat body. Other possible side-effects of a long term and/or high dosed treatment with cortisone are: diabetes mellitis (diabetic), high blood pressure, thrombosis, problems with the airways (e.g. difficulty, panting, pneumonia) or oedema (fluid retention) The eyes can also be affected (corneal ulcers).
Furthermore there is the possibility of decreased fertility (heat), and testicles that grow smaller.
Psychological symptoms are also possible, e.g depression or anxiety.
In pups growing disorders occur, because cortisone i.a. inhibits the growth hormone of the pituitary gland.
Diagnosis Cushing syndrome.
Your vet will probably suspect Cushing's because of the appearance of your dog. Therefore he will carry out specific blood and urine tests, make x-rays, do an ultrasound and possibly make a CT-scan to localize the tumor.
Treatment Cushing syndrome.
Because cortisol influences every cell in the body, it is important to start treatment as soon as possible.
Regular medicine can try to remove the tumor on the adrenal gland. If this is possible depends on the location of the tumor. Surgical removal of a pituitary gland tumor is usually extremely difficult, because the pituitary gland is not easily accessible and the tumor is very small (the size of a pin-head). The surgery is not done very often and only in specialized veterinary clinics. That is why, most of the time, tablets are prescribed. Either Lysodren (also used as a cancer medicine with lots of side effects) or Trilostane, a new therapy that has a much higher tolerance. But there are also side effects when using Trilostane, mild ones like weakness, vomiting, diarrhoea, anorexia or muscle tremors, but it can also cause kidney failure or sudden death!
Chinese herbal medicine uses the herbal formula Cushing complex in the treatment of Cushing’s syndrome. This formula curbs the production of cortisol in a natural way, without causing harmful side effects like Lysodren or Trilostane.