Role of Adrenal Gland in Dogs Health
The adrenal glands are a pair of glands that play an important role in different physiological and metabolic functions in a dog’s body. The hormones that they produce influence and regulate important bodily processes such as blood pressure, vascular tone, elimination, and retention of water and electrolytes, all of which have a significant impact on your dog’s health. This is why adrenal glands are considered essential for life.
Dog’s Adrenal Glands
The adrenal glands are a pair of small glands located in the abdominal space, near the left and right kidneys. They are so small that for centuries, they were ignored by anatomists!
The gland consists of two parts: an outer cortex and an inner medulla. These parts are composed of different cells and tissues, which originated from different embryonic structures, and have entirely different functions in relation to influencing metabolic pathways in the dog’s body.
The outer cortex is mostly yellow in appearance and has striations that are radially directed. The cortex is composed of three zones, namely the Zona Glomerulosa, Zona Fasciculata, and Zona Reticularis. Each zone is responsible for producing different hormones that play an important role in influencing functions and metabolic pathways in the body. The inner medulla, on the other hand, appears darker and more homogenous.
Adrenaline and Norepinephrine Production
The inner portion of the adrenal glands, called the medulla, is responsible for the production of two very important hormones when the dog is under severe and acute stress. The adrenal medulla is the main component responsible for the animal’s “fight or flight” response mechanism.
One of the hormones produced by the adrenal medulla is epinephrine, commonly known as adrenaline. This hormone is often considered the “fight or flight” hormone and plays an important role in influencing how the body responds to acute stress.
When a dog is subjected to a severely stressful condition, it stimulates the glands to produce adrenaline as a response. The hormone causes the animal’s heart rate to increase and force stronger cardiac contractions which help improve blood flow to the muscles and brain.
It also diverts energy consumption and blood flow from the gastrointestinal system to focus on the animal’s immediate need to either “fight or flee”. Stomach and intestinal activity slow down and stored glucose in the liver, in the form of glycogen, is converted back into glucose. This can provide an immediate source of energy for the dog should it be needed.
The second hormone produced by the adrenal gland’s inner medulla is norepinephrine, also known as noradrenaline. It’s also a hormone produced by the adrenal gland in response to stress. Norepinephrine stimulates the blood vessels to increase blood pressure and heart rate, much like adrenaline does. It also stimulates the dog’s central nervous system, making them more alert during the “fight or flight” mechanism.
Steroids and Other Hormones
As mentioned, the outer adrenal cortex has an entirely different function from the medulla. It produces a different set of hormones that have varying effects on the dog’s body. In general, the adrenal cortex is the main part responsible for the production of glucocorticoids and sex hormones. The cortex is divided into three layers or zones, each responsible for producing a specific metabolic hormone.
The outer zone, called the Zona Glomerulosa, produces and secretes mineralocorticoid hormone. Mineralocorticoids are a subgroup of corticosteroid hormones that are responsible for maintaining electrolyte balance in the dog’s body. The most potent mineralocorticoid, called aldosterone, influences the transport of important ions and electrolytes, such as sodium and potassium, inside the kidney tubules. It is responsible for accelerating the elimination of potassium and the retention of sodium which ultimately helps maintain the dog’s electrolyte and water balance.
The middle zone, called the Zona Fasciculata, is responsible for the production and secretion of cortisol and corticosterone. These glucocorticoid hormones have a very wide range of physiological effects that directly influence the health of the dog. Glucocorticoids greatly influence the animal’s immune system, inflammatory processes, and metabolism of different nutrients such as carbohydrates, fats, and proteins.
Cortisol and corticosterone both suppress immune and inflammatory responses of the dog’s system, helpful in cases of physical trauma or inflammatory conditions. These can be harmful as they also diminish the animal’s ability to fight off bacteria and viruses, making them vulnerable to infections.
Glucocorticoids also stimulate the production of glucose and increase the blood sugar level of the dog. Additionally, it slows down the body’s fat production and stimulates the breakdown of fat tissues in the body, releasing fatty acids and glycerol into the animal’s system. All of these result in readily available sources of energy for the animal.
The inner layer of the adrenal cortex, called the Zona Reticularis, is responsible for the secretion of adrenal sex hormones. Most sex hormones are produced by the reproductive organs, but a relatively small amount is produced by the adrenal cortex.
These include progesterone, androgens, and estrogen hormones. The effect of these hormones originating from the adrenal cortex is often insignificant, especially in intact dogs, because the majority of the sex hormones in the dog’s body are produced by the ovaries or testes. However, once a dog is spayed or neutered, these sex hormones produced by the adrenal glands may take on more significance in terms of physiological effects in the animal’s body.
How adrenal glands benefit your dog
The adrenal glands secrete a range of hormones that regulate many systems throughout a dog’s body. Here are the primary functions of adrenal glands that keep your dog healthy.
- Fight-or-flight response: When your dog feels threatened, the adrenal glands release two hormones: adrenaline and noradrenaline. They work in tandem to help the body either run away or stay and fight. These hormones trigger a series of physiological responses like faster heart rate, stalled digestion, increased blood flow to the muscles and metabolizing glycogen for energy.
- Stress management: The adrenal glands produce a group of hormones called glucocorticoids. The main hormone in this group is cortisol. Adrenal glands release cortisol in order to manage your dog’s response to stressful situations. Healthy levels of cortisol are associated with reduced stress in the presence of triggers like strangers, other animals and loud noises.
- Metabolic system: Cortisol is also responsible for digesting carbs, fat and protein. In times of stress, cortisol draws from glycogen stores and tells the liver to convert it to glucose. Similarly, cortisol can make fat reserves emit fatty acids, which the liver also converts into a usable form of energy. Cortisol metabolizes macronutrients in response to stress because the body needs energy in order to combat the perceived threat.
- Water retention: Aldosterone is another key hormone produced in the adrenal glands. It encourages the kidneys to hold onto sodium, which allows the body to absorb more water. In other words, this hormone balances the body’s water supply. Aldosterone also retains electrolytes, which are necessary for proper hydration. The hormone aids hydration by helping electrolytes such as sodium and potassium phase through cell walls.
Addison’s disease
As with any part of the body, adrenal glands are susceptible to diseases that prevent them from properly functioning. One such issue affecting the glands is Addison’s disease. Dogs are diagnosed with Addison’s disease when their adrenal glands don’t produce enough aldosterone or cortisol. Low levels of these hormones may cause metabolism issues or severe dehydration, both of which are fatal in dogs.
The tricky thing about Addison’s disease is that the associated symptoms could easily look like any number of illnesses. Your vet will have to rule out these other illnesses before diagnosing your dog with Addison’s disease.
Any combination of the following symptoms can appear in dogs with this adrenal gland issue:
- Lethargy
- Lack of appetite
- Gastrointestinal upset
- Hair loss
- Increased thirst and urination
- Irregular heartbeat
Unfortunately, there’s no way to prevent Addison’s disease. The most common treatment option is a daily pill that provides the adrenal glands with adequate hormone levels. Dogs who take replacement hormone medication generally have a good prognosis and can live long, normal lives. Pet parents who observe the signs of Addison’s disease should consult a vet right away because a life-threatening illness could be at stake.
Cushing’s disease
By contrast, Cushing’s disease occurs when the adrenal glands produce too many hormones. The disease usually results from a benign or malignant tumor that grows either on the adrenal glands or pituitary gland. When tumors form on the pituitary gland, adrenocorticotropic hormone (ACTH) stimulates the adrenal glands to produce dangerously high levels of cortisol.
Cushing’s disease is often confused with Addison’s disease because they both affect the adrenal glands and share overlapping symptoms. However, Cushing’s disease is associated with additional signs.
Here are some of the many symptoms often seen in dogs with Cushing’s disease:
- Increased appetite
- Increased thirst and urination
- Pot belly due to increased fat
- Recurring skin and bladder infections
- Dark spots on the skin
There’s not much pet parents can do to prevent tumors from growing on the pituitary or adrenal glands. Your vet might recommend surgically removing the tumor, although this procedure tends to be more successful if the tumor is benign. In addition to surgery, dogs can take an oral medication that manages ACTH and cortisol production.
Since the adrenal glands play so many roles, it’s no wonder that diseases of these glands quickly become serious. Adrenal glands are very small, but their importance is hard to overlook. The best thing a pet parent can do to protect their dog’s adrenal glands is schedule a vet appointment as soon as they display any of the above-mentioned symptoms. When you prioritize adrenal gland health, you prioritize your dog’s full-body wellness.
Compiled & Shared by- Team, LITD (Livestock Institute of Training & Development)
Image-Courtesy-Google
Reference-On Request.
