The adrenal glands are located just in front of the kidneys. You will recognise them from when we discuss the stress response in both humans and dogs.
The adrenal gland has 2 parts—the cortex and the medulla.
The adrenal cortex is subdivided into 3 layers, and each layer produces a different set of steroid hormones. The outer layer produces the mineralocorticoids, which help regulate sodium and potassium salts. The middle layer produces glucocorticoids, which are involved in metabolising nutrients and also reducing inflammation and immune responses. Finally, the inner layer produces sex hormones such as oestrogen, progesterone, and androgens.
The adrenal medulla plays an important role in response to stress or low blood sugar levels in the body. It releases adrenaline and noradrenaline, both of which increase heart rate and blood pressure, increase blood sugar and slow digestion; the hallmark responses when us or our dogs are exposed to a stress trigger.
The adrenal glands are part of the endocrine system – which is simply a system of glands that release chemical messengers called hormones. The endocrine system influences almost every cell, organ, and function in the body.
So, if there is any issue in any part of it, things can start to go awry in the body.
The two most common ways in which adrenal glands cause health issues are by producing too little or too much of certain hormones, which leads to hormonal imbalances.
Cushing Disease
Cushing disease, also referred to as hyperadrenocorticism, is a common endocrine disease in adult dogs. It is when there is increased production of adrenal gland hormones and there are a few reasons why this may occur.
The most common cause (85% to 90% of cases) is a tumour in the pituitary gland. The pituitary tumour produces a hormone that triggers excessive development of the adrenal gland.
Less common (10% to 15% of cases) is a tumour in the adrenal glands themselves.
But there is also evidence suggesting that long-term use of corticosteroid drugs (to decrease inflammation or treat an immune disorder) can also cause over-production of hormone secretion.
Poodles, dachshunds, beagles, german shepherds, and many terrier breeds are predisposed to developing Cushing's though it isn’t yet clear what the genetic link is. A predisposition is particularly noted in the Dachshund. Females are also slightly more predisposed than males (60% vs. 40%).
Signs and Symptoms include:
- increased thirst and urination
- increased appetite
- heat intolerance
- lethargy
- a “potbelly”
- panting
- obesity
- weakness
- thin skin
- hair loss
- bruising
On the other side of the scale, we have Addison Disease.
Addison Disease
Addison disease, also called hypoadrenocorticism, is caused by a deficiency of adrenal gland hormones. It is most common in young to middle-aged dogs. The cause is usually not known, but an autoimmune condition in which the body destroys some of its own tissue is typically noted. The adrenal gland can also be destroyed by other conditions, including medications used to treat Cushing disease.
In Cushing disease, the secretion of certain hormones is reduced, which affects the levels of potassium, sodium, and chloride in the blood. Potassium gradually builds up in the blood and may cause the heart to slow down or beat irregularly. Some dogs have such a slow heart rate that they can become weak or go into shock. Decreased production of other hormones results in moderately low blood sugar.
Signs and Symptoms include:
- repeated episodes of vomiting and diarrhoea
- loss of appetite
- dehydration
- gradual loss of body condition
- Pale oral membranes (tacky)
- Decreased capillary refill time.
Although signs can be hard to identify whilst Addison’s disease is developing, shock and evidence of kidney failure can develop suddenly.
Addison’s Disease may be inherited in Standard Poodles, West Highland White Terriers, Great Danes, Bearded Collies, Portuguese Water Dogs, and others. Although the disease can be seen in any breed, sex, or age, it is most common in young, female, adult dogs.
Both of these conditions require treatment from a vet. But they do show us how intertwined the body is, and that if we want to support our dog’s health, we need to consider all their bodily systems.
For the dog who isn’t experiencing adrenal crisis, but warrants some endocrine TLC, there are certain herbs that can support adrenal function; Dandelion, Nettle, Withania, Bacopa, Turmeric, Astragalus, Milk Thistle & Liquorice.
Written by Lisa Hannaby - Bsc. Psych. Hons, MSc Human Nutrition