Cushing’s Disease, also Hyperadrenocorticism

Cushing’s Disease

What is it?

In Cushing’s disease, a certain hormone called cortisol becomes overproduced. This hormone actually comes from the adrenal glands. As part of the body’s normal response to stress, it activates a biologic system called the Fight & Flight response. In layman’s term, it is the experience when being under pressure or when dealing with great stress like when you are inside a building filled with flames. You will then be surprised that you suddenly got the guts to jump off from the top of the roof just to escape the fire. In this example, you most likely had a surge of what is called as an ‘adrenaline rush.’

But in Cushing disease, this rush is specifically the release of cortisol – the stress hormone. When cortisol is released, the body responds accordingly by boosting its functions like supplying more energy or making the muscles contract more so as to generate more strength. Even if the surge of cortisol is considered normal, there are some cases wherein the blood levels of this hormone become too much to handle or when it becomes elevated for long periods of time. As a result, it brings about to many undesirable bodily changes. Otherwise known as hyperadrenocorticism, Cushing’s disease is a debilitating disorder.

Cushing’s Disease – The Signs

In as much as humans can suffer from this disease, dogs too have a high likelihood of experiencing Cushing’s disease. As a result, he will end up drinking too much fluid that leads to putting in more weight. Also, there can be some unexpected changes with the dog’s coat like when the hair becomes thin. But in some cases nonetheless, dogs can have an abnormally thickened coat underneath or at the flank region as a reaction to increased cortisol levels. Still involving the integumentary system, the dog’s skin may also appear thinner than ordinary most especially the ones at the abdominal area. There is also a great chance for crusting and scab formations.

Although cortisol generates added strength for the muscles during stress, the prolonged release of this hormone can cause otherwise. The muscles and the abdomen will look saggy as these areas become weakened. The limbs and the back will eventually sag as well.

In addition, when cortisol is constantly released into the bloodstream it will have a direct effect on the immune system as there will be immune suppression. Infections, specifically those involving the skin, are more commonly noticed. In bitches, they may end up having a series of bladder infections (also known as cystitis).

What are the causes?

The pathology behind Cushing’s disease is brought about by the adrenal glands producing more cortisol than what is actually needed. So the question must be targeted on what’s causing the gland to overproduce the said hormone. In this regard, there are only two most likely reasons.

In most cases, about 90% of all Cushing’s diseases, a growth at the master gland (Pituitary gland) triggers the adrenal gland to produce more cortisol. This pituitary gland is called the master gland because it has the power to command all other glands to regulate the production of their hormones. It releases messenger hormones that tell the adrenal gland to continue producing cortisol. With regard to the growth, it actually has the potential of becoming a large tumour that can press against the brain causing more damage. But oftentimes, the growth is rather small.

The second cause is a tumour at the adrenal gland. Adrenal tumours, although less likely occurring, can become malignant. As a result it can metastasize or spread in other regions throughout the body. Instead of being commanded by the messenger hormones from the master gland, this tumour is capable of producing its own cortisol that adds up to the blood levels of the said hormone. As a result, there is an uncontrollable flow of cortisol in the bloodstream.

Cushing’s disease – the Diagnosis

Even if you have noticed the excessive thirst in your pet, it is still best to submit the canine to a blood test to verify if there are abnormal blood values. Although a general blood screening may serve the purpose, more specific tests should be done for confirmation sake.

One of the specific tests is called the ACTH stimulation test. It is called as such because it makes use of ACTH – the messenger hormone that triggers the adrenal gland to secrete cortisol. This test is said to be the fastest and the most frequently used test for Cushing’s disease diagnosis. In this test, two samples of blood are obtained. One sample is procured right before administering ACTH then the second sample will be obtained an hour after the administration of the said hormone.

The second specific test is called Dexamethasone Suppression test. This time, three blood samples are procured within a period of 8 hours. On top of that, steroids will also be administered via injection. Moreover, there is actually a third test that will identify the actual cause of the disease so that it can be identified if a growth at the pituitary gland or a mass at the adrenal glands is causing the disorder. This test is similar to Dexamethasone Suppression but only necessitates higher doses of injectable steroids.

How is it treated?

Surgery involving the extraction of the tumour is possible if the growth is only situated in one of the adrenal glands and if it is benign (not cancerous). Performing surgery for pituitary gland growths is riskier because it literally involves brain surgery.

Mitotane is the drug of choice for Cushing’s disease. Because it has the potential of damaging the adrenal glands, its dose will be controlled or tapered down so as to prevent the occurrence of adverse effects. If too much adrenal destruction occurs because of the drug, then hormone replacements may be prescribed. Normally, it is given daily for the first round of treatment and then weekly so as to offer just the right amount of suppression to the gland.

Because of the debilitating nature of this disease, pet owners often don’t seek any advance medical care once they know that their pets have this disorder. It is because the therapy is long term and that it will obviously require a lot of financial resources.

Disclaimer

This pet health article is for reference only.

If your pet is showing any symptoms or distress, and you suspect your pet is ill CONTACT YOUR VET IMMEDIATELY.