Cortisol, also known as the stress hormone, plays a vital role in the dog's endocrine system. Consisting of a vast network of glands, tissues, and hormones, the endocrine system is responsible for many bodily functions and processes.
Therefore, it is safe to assume that despite its popular name, the stress hormone does more than managing the dog's anxiety levels.
In this article, we will explain what cortisol is in more detail. We will also discuss how it impacts dogs psychologically and physiologically, and finally, we will talk about how too little or too much can cause health conditions.
Discovering the Roles of Cortisol
Based on its nature, cortisol is a steroid hormone critical for several body processes. Because of its importance, there are many synthetic versions modern medicine uses to treat different health issues.
The most popular role of cortisol is regulating stress levels and danger responses, hence the stress hormone's layman name.
Other significant roles include amplifying the body's immune reactions, modifying blood pressure, managing healthy blood sugar levels, and inhibiting inflammatory processes.
Most of the body's cortisol supply is produced by the adrenal glands located above and in front of the dog's kidneys. The adrenal glands produce the hormone, but its production rate depends on the hypothalamus and pituitary gland.
When there is not enough cortisol in the bloodstream, they produce and send a so-called adrenocorticotropic hormone (ACTH) that will signal the adrenal gland to start working. Once synthesized, the cortisol is released into the bloodstream and starts working.
How much cortisol will be produced depends on several factors and is highly variable. The body determines the need for cortisol based on a set of physical, physiological, and environmental stimuli.
Too Much Cortisol Leads to Cushing's Disease
Cushing's disease is the medical term used to indicate the adrenal glands when they are overproducing cortisol, thus putting the dog at risk of several potentially life-threatening complications. Cushing's disease is also known as hyperadrenocorticism.
Cushing's Disease Causes in Dogs
There are three possible Cushing's disease causes in dogs: pituitary tumors, adrenal tumors and excess use of synthetic cortisol medications. Let's take a look at each of them.
- Pituitary tumor. This is a benign or malignant tumor on the pituitary gland leading to excess production of ACTH and consequently high cortisol levels in the bloodstream.
- Adrenal tumor. This is a benign or malignant tumor on the gland itself, making it overproduce cortisol regardless of the body's needs and ACTH levels
- Iatrogenic Cushing's this condition is caused by an irresponsible and excess use of synthetic cortisol versions.
Signs of Cushing's Disease in Dogs
Dogs suffering from Cushing's disease will show one or more of the following signs and symptoms:
- Increased appetite
- Increased thirst and frequent urination
- Enlarged abdomen with a potbellied appearance
- Thinning of the skin
- Hair loss
- Muscle weakness
- Lethargy and depression
Dogs showing these red flags require urgent veterinary attention. This is because Cushing's disease increases the risk of several potentially fatal complications like high blood pressure, diabetes, blood clots, and kidney failure.
Diagnosis of Cushing's Disease in Dogs
As in any other case, when there is suspicion for Cushing's disease, the vet will start with a full physical examination, including blood panels (complete blood count and biochemistry) and urinalysis.
To make a more specific evaluation of how the adrenal glands work, the vet will perform exams like adrenal low dose testing, adrenal function tests, and dexamethasone suppression tests.
To support the findings and rule out other possible conditions, the vet will recommend ultrasound or, if possible, an MRI.
Treatment of Canine Cushing's Disease
Treating Cushing's disease in dogs is usually based on the use of medications that can decrease the cortisol levels in the bloodstream. This is a life-long treatment and requires consistent use of the prescribed medications.
The only way of genuinely curing the condition and eliminating the need for medication administration is tumor removal. However, this approach is rarely applicable as the surgical procedure is both complex and risky.
The exact treatment depends on the underlying issue leading to cortisol overproduction.
Treatment for Pituitary Tumors
In terms of treatment, the pituitary-dependent Cushing's disease is the most challenging form of hyperadrenocorticism. There are only two drug options – trilostane and mitotane.
Both meds are synthetic steroids capable of inhibiting steroid production. However, long-term use is associated with severe side effects, thus requiring close monitoring.
Treatment for Adrenal Tumors
In cases of an adrenal tumor, the vet will recommend abdominal surgery to determine the type of tumor and, if not malignant, attempt removal.
If the tumor is benign and can be successfully removed, there is a good chance your dog will be able to continue disease-free.
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Treatment for Iatrogenic Cushing's disease
In cases where the condition is caused by steroid overuse, the simple solution would be discontinuation. However, once the steroid treatment is discontinued, the disease for which the therapy was used in the first place will reappear.
Dogs with iatrogenic Cushing's disease need lifetime monitoring of several blood parameters and routine checkups.
Cushing's Disease Prognosis
Diligent observation, long-term management, and close collaboration with the vet can help keep Cushing's disease under control. Thanks to the many advances, dogs with hyperactive adrenal glands can be successfully managed with few and minimal side effects.
However, once again, this would require regular checkups, parameter tests, and frequent vet visits.
Dogs with unmanaged Cushing's disease experience relapses. The prognosis is also poor for dogs with untreated Cushing's as the disease usually triggers organ failures and other life-threatening complications.
Too Little Cortisol Leads to Addison's Disease
Addison's disease is the medical term indicating when the adrenal glands are producing inadequately low amounts of cortisol.
Same as Cushing's disease, Addison's disease puts dogs at a higher than average risk of developing several potentially fatal health issues and complications. Addison's disease is also known as hypoadrenocorticism.
Causes of Addison's Disease in Dogs
Addison's disease in dogs can be classified into two groups based on the underlying culprit: primary Addison's and secondary Addison's.
- Primary Addison's is caused by immune-mediated destruction of the adrenal gland cells. This happens when the immune system accidentally recognizes the adrenal tissue as foreign and decides to destroy the potential threat. The adrenal tissue can also be damaged by infections, trauma, and certain types of cancer.
- Secondary Addison's is usually triggered by tumors or faulty functions of the pituitary gland. This secondary form of hypoadrenocorticism can also occur if a dog treated with steroids was abruptly taken off the meds (also known as iatrogenic Addison's). Dogs with iatrogenic Addison's experience a temporary lack of adequate cortisol production.
Interestingly, certain dog breeds are more likely to develop Addison's disease than others. The list of dog breeds predisposed to this hormonal imbalance includes:
- Bearded Collies
- Great Danes
- Labrador Retrievers
- Nova Scotia Duck Tolling Retrievers
- Portuguese Water Dogs
- Standard Poodles.
Signs of Addison's Disease in Dogs
Sadly, the signs of Addison's disease are non-specific, vague, and often occur in episodes – they wax and then wane without warning. Therefore, by the time veterinary attention is sought, the condition is already well advanced in most cases.
Here are some of the frequently reported signs and symptoms of Addison's disease:
- Increased thirst
- Increased urination
- Intermittent shaking
- Weight loss.
In some dogs, the condition can take a more serious course and trigger a so-called Addisonian crisis manifesting with severe bouts of vomiting, diarrhea, and collapse. This form is considered an emergency, thus requiring immediate hospitalization and adequate supportive care.
Diagnosis of Addison's Disease in Dogs
Once again, everything starts with a general physical examination. Addison's disease is suspected in dogs with a history of unexplained diarrhea and vomiting bouts.
To make a more distinct analysis, the vet will recommend checking the dog's electrolyte levels and perform an ACTH-stimulation test. The ACTH-stimulation test consists of measuring the cortisol levels before and after supplementing the dog with injectable, synthetic ACTH form.
The vet is likely to order a series of additional tests like radiographs, ultrasounds, electrocardiograms, or even MRI and CT scans. These tests will help eliminate other potential diagnoses and evaluate the extent of the hypoadrenocorticism complications.
Canine Addison's Disease Treatment Options
The treatment of Addison's disease in dogs is based on a drug called desoxycorticosterone pivalate (DOCP). DOCP is FDA-approved for the treatment of Addison's disease in dogs.
Available in an injectable form, DOCP is administered every three to four weeks based on the dog's individual needs. In some cases, the DOCP use is combined with oral administration of corticosteroids.
The best thing about DOCP is that it allows dogs to live completely normal lives and does not warrant the need for diet and lifestyle changes.
Addison's Disease Prognosis
Once the diagnosis is made, the dog is put on proper medications, and the cortisol levels are under control, the prognosis for most dogs is excellent.
However, the long-term prognosis usually depends on how promptly the treatment was initiated and the dog's overall health status.
The Importance of Cortisol for Dogs
As a steroid hormone and vital part of the endocrine system, cortisol fights off stress and infection and is a weapon against inflammation. Basically, it amplifies the body's ability to resists damaging and pathological factors.
Problems with the adrenal glands result in an inability to either synthesize or utilize cortisol. Once the cortisol levels are below or above the ideal range, the dog will start experiencing devastating symptoms varying from dehydration, increased thirst, and weak muscles to severe skin issues, debilitated immune system, and organ failure.
Today, with the advances in modern veterinary medicine, it is possible to manage adrenal gland problems. However, the managing need is life-long and will require particular regimens and lifestyle changes.