The Role of Cortisol in Pets

As cortisol is the key contributor to Cushing’s syndrome, we have written quite a bit about it in that context already.  However, in this post, we are going to step back a bit and focus on what it does in non-Cushing’s dogs as well.  What other diseases are associated with cortisol?  And, if it is responsible for these diseases, then why do dogs, humans and other animals produce it in the first place?

What is Cortisol?

Cortisol is commonly known as a stress hormone. It plays a crucial role during stress in dogs, cats and, yes, humans too. It is one of the hormones produced in the adrenal cortex (the outer layers of the adrenal glands).  Cortisol is essential to life and, in particular, to the proper functioning of many body systems.  Some of these include:

Regulation of the immune system

Cortisol is an anti-inflammatory agent capable of tamping down inflammation both systemically and locally.  This is why it is contained in so many topical anti-itch creams, like Cortisone cream.  If you’ve ever been injected to treat or prevent inflammation, it was probably with a form of cortisol (hydrocortisone, prednisone, prednisolone, just to name a few).  Similarly, the main ingredient in steroid inhalers, such as Flovent is a form of cortisol.  Thus, cortisol is one of the various agents in the body that keep the immune system properly tuned so that it identifies real threats and ignores ones that aren’t.  In the absence of some mechanism to keep the immune system at bay in the presence of non-threats, the immune system may attack the body’s own tissues, resulting in discomfort or disease.

Stress response

Cortisol assists the animal’s body in tackling stressful situations. During times of stress (whether from attacking animals, malnourishment, social or work situations or other cause), cortisol levels rise.  This results in the release of stored sugars, the manufacture of sugars from muscle tissue, reduction of uptake in glucose by muscle cells, increases in heart rate and blood flow and increase in breathing rate.  These effects prepare the body to mount a flight or fight response by conserving maximum fuel for use by the brain, increasing oxygen available throughout the body and otherwise preparing the body to react to a stress event with maximal vigor.

Energy and Metabolism regulation

To keep energy and metabolism in balance, cortisol is of prime importance. During times of increased demand (such as when exercising or engaging in other physical activity), cortisol promotes the breakdown of glycogen to glucose to ensure the body maintains sufficient glucose to fuel the activity. Cortisol also regulates the metabolism of proteins and fats, both in times of increased activity and otherwise.  

What happens if the body doesn’t produce enough cortisol?

Given cortisol’s essential role in so many bodily systems, you can see that either too much or too little cortisol production can, if persisting over a long term, have significant impacts on the body and can lead to health issues.  Long-term cortisol deficiency leads to a condition called Addison’s disease.

Addison’s Disease

Cortisol deficiency (and Addison’s disease) may be caused by:

• Immune-mediated (or auto-immune) destruction of the adrenal glands
• Direct damage or trauma to the adrenal glands
• Infection of the adrenal glands
• Cancer or other tumor inside or that presses on the adrenal glands
• Any of the above that affect the pituitary gland (hypophysis) or hypothalamus (instead of or in addition to affecting the adrenal gland)
• Long term use of steroids

Breeds

Certain breeds of dogs are predisposed to development of Addison’s disease, including:

• Great danes
• Bearded collies
• Portuguese water dogs
• Standard poodles
• Labrador retrievers
• Duck tolling retrievers
• Leonbergers

What are the clinical signs of underproduction of cortisol in dogs?

If your pet is not producing enough cortisol, this may manifest itself in a variety of signs.  However, these signs are non-specific and vague, and that’s why it is difficult to diagnose without testing. Some important signs include:

• Lethargy
• Increased urination
• Vomiting
• Diarrhea
• Increased thirst
• Unexplained weight loss
• Intermittent body shaking episodes

If your dog is exhibiting any of these signs, your veterinarian will test blood and/or urine for cortisol levels and may conduct other tests to confirm an Addison’s diagnosis.

What would happen if cortisol elevated acutely?

The fight-or-flight response was developed early in our (and our pet’s) common evolutionary history.  It was a response to immediate threats lasting just seconds or minutes, not hours or days let alone years.  Thus, for example, a brief elevation in glucose levels wouldn’t be expected to have any impact on a body at all.  The body is well-adapted to handle that circumstance.  However, if glucose levels stay elevated for months and years, insulin resistance and metabolic conditions are a near inevitability.  So, it is useful to think about cortisol both in terms of short-term effects and long-term effects.

Here are some of the short-term effects of increased cortisol levels:

1. Suppressed Immune Function: An abrupt rise in cortisol levels can impair immunity, leaving pets more vulnerable to sickness and infection. It weakens the immunological response, making the body less capable of successfully warding off invaders.
2. Elevated Blood Sugar Levels: Cortisol promotes the conversion of glycogen reserves into glucose, raising blood sugar levels. When cortisol levels are elevated suddenly, blood sugar levels can rise quickly. If this trend is maintained, it may eventually lead to the onset of diabetes or insulin resistance.
3. Digestive Problems: High cortisol levels might impair the regular operation of the digestive system. It may lessen appetite, causing a pet to eat less and maybe lose weight. Additionally, it might interfere with how nutrients are absorbed and raise the possibility of gastrointestinal issues, including vomiting, diarrhea, or constipation.
4. Impairment of Cognitive Function: Dogs and cats with high cortisol levels may experience cognitive impairment. High cortisol could result in behavioral changes such as increased anxiety, agitation, or trouble concentrating. A sudden rise in cortisol levels might make it harder to learn new things and retain information.
5. Muscular atrophy: Acute cortisol rise can cause muscular tissue to break down, which can cause muscle atrophy or weakness. This might be especially concerning for animals going through stressful conditions or suffering from serious illnesses.

What would happen if cortisol elevated chronically?

Chronically elevated cortisol levels lead to Cushing’s syndrome.  The same types of damage to the adrenal gland, pituitary gland or hypophysis that lead to Addison’s disease may instead lead to Cushing’s syndrome—there is no way to predict whether, for example, a tumor pressing on a gland will cause that gland to over-produce, under-produce or not change production of cortisol.  As with Addison’s disease, the health and well-being of dogs and cats may be significantly impacted when cortisol levels are persistently raised. The following are some possible effects of sustained cortisol elevation:

1. Increased Risk of Obesity: In dogs and cats, prolonged cortisol increase can lead to weight gain and obesity. Cortisol encourages fat storage and the breakdown of muscular tissue, especially in the stomach area. This may lead to excessive weight gain and a higher risk of diseases, including diabetes and joint difficulties.
2. Cortisol is involved in the regulation of skin health: Chronic cortisol rise can cause dryness, thinning, and increased susceptibility to infections in the skin. Skin allergies, rashes, and delayed wound healing can all occur in pets.
3. Behavioral and psychological effects: Chronic cortisol increase can have an effect on a pet’s behavior and mood. Later on, it progresses into anxiety, irritability, restlessness, and aggression, along with changed sleep patterns.  
4. Immune system suppression: A long-term increase in cortisol levels can impair immunity, leaving pets more prone to allergies, infections, and autoimmune diseases. Increased susceptibility to numerous ailments results from the immune system’s decreased ability to fight off germs.

Final thoughts

Cortisol dysregulation in dogs and cats must be addressed in order to lessen its negative consequences. It is critical to identify and address the underlying causes of chronic stress or medical issues. A veterinarian can order diagnostic tests to determine cortisol levels and provide a treatment plan that is suited to your pet’s individual needs. Lifestyle changes, stress reduction techniques, medication, and addressing any underlying health issues are all possible strategies.

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