It’s Monday Marvels, and today we will be introducing the dog’s adrenal glands. Like some other dog body parts that for the most part live in the shadow, you likely don’t hear much about the adrenal glands unless they start giving problems. In dogs, the adrenal glands are responsible for secreting important hormones, but sometimes things can get a bit out of whack in the hormonal department. By getting more acquainted with these glands, we can better understand their important role in a dog’s overall state of health and sense of well being. So for Monday’s Marvels let’s see what the adrenal glands have to say.
Hello, it’s your dog’s adrenal glands talking! Our name derives from the fact that we are located right in front of your dog’s kidneys. The term “renal” indeed comes from the Latin word “renes ” which stands for kidneys” while the prefix “ad” comes from the Latin word “near.” Therefore put 2 and 2 together and you’ll figure out that adrenal means “near the kidneys.” At a first glance, if you look at our structure we may look like two glands, one on the left, and one of the right, but actually, we’re made of some distinct parts. To better give you an idea, imagine a chocolate-covered peanut. The peanut being one part (the adrenal medulla), and the chocolate on top being another, (the adrenal cortex). That’s how we are structured. What are our main functions? We actually have several, so hold tight as here are some.
The adrenal medulla, the inner peanut portion of us, is responsible for secreting the hormones epinephrine (adrenaline) and norepinephrine (which increases blood pressure) into your dog’s bloodstream. You see, when your dog feels threatened from something, his sympathetic nervous system kicks in, triggering what is known as the “fight or flight response.” Basically, his body gets in a hyper reactive state so it’s ready to spring into action and up his chances for survival. For the sake of comparison, it’s that short-term stress reaction you may feel when you’re camping and see a bear that has come too close for comfort.
Your dog’s heart will therefore beat faster, his blood pressure rises, the airway passages dilate, blood is sent to the muscles and his senses become more acute. At the same time, his gastrointestinal function decreases, which is why he may not be interested in that slice of baloney you dangle in front of his face when he’s extra worried about something. Even after the scary event has passed, it may take some time for your dog’s body to recover from such an excited state considering that these hormones tend to stick around in the bloodstream for some time.
The outer portion of us, the adrenal cortex, comprises several layers, with each layer being responsible for different tasks. To have a better idea, imagine our outer portions as the layers of an onion. My outermost layer is the zona glomerulosa, then, sandwiched somewhere in between is the zona fasciculata, and finally, our inner portion is the zona reticularis. To have a better idea, see the picture on the side. Now, let’s take a closer look at the different roles these layers play, shall we?
- Raising Your Dog’s Blood Glucose
The zona fasciculata, the middle layer, is responsible for producing glucocorticoid hormones. These hormones include cortisone, cortisol and corticosterone which share the ability to raise your dog’s levels of blood glucose, maintain blood pressure and help the body deal with the effects of stress. Glucocorticoids also act as natural steroids, suppressing any inflammatory and immunologic responses.
- Regulating Your Dog’s Minerals and Salts
The outermost layer, the zona glomerulosa, is responsible for regulating the amounts of important electrolytes under the form of minerals and salts in the body. Aldosterone, the main mineralocorticoid hormone, regulates the right balance of salt, potassium and water and helps control blood pressure. You see, when levels of potassium are too high, they must be lowered as potassium can become toxic at high levels, so aldosterone works on keeping its levels under control.
- Producing Dog Sex Hormones
Finally, the inner most layer, the zona reticularis, is responsible for the production of small amounts of the sex hormones androgen, progesterone and estrogen.
While I try to do my best in producing hormones as needed, sometimes things can get out of whack. If my adrenal cortex happens to produce too much cortisol, affected dogs may develop what is known as “Cushing’s disease,” also known as hyperadrenocorticism. In a normal, healthy dog, a normal amount of cortisol helps the body adapt in times of stress and regulates proper body weight and tissue structure, but too much of a good thing leads to the weakening of the dog’s immune system and a predisposition to infections and disease, explains Ann Stohlman, a veterinarian working for the FDA’s Center for Veterinary Medicine. Why do I produce so much cortisol? Good question! The Merck Manual states that 85 to 90 percent of the time, it’s due to a tumor in the pituitary gland. Less commonly it’s due to either a tumor in my glands or the long term use of steroid drugs.
If instead, my adrenal cortex produces too little adrenal gland hormones, affected dogs may develop what is known as “Addison’s disease,” also known as hypoadrenocorticism. Why do I produce too little of these hormones? In this case, we can blame some auto-immune condition, where the dog’s body mistakenly destroys some of its own tissues, infections in the gland or some form of cancer. When I secrete too little aldosterone, the levels of potassium, sodium, and chloride in the dog’s bloodstream are no longer regulated and we already talked about how toxic potassium can be if there’s too much.
Did you know? Dogs can be also prone to adrenal fatigue. According to veterinarian Randy Kidd, chronic overstimulation of the adrenal glands may lead to adrenal fatigue and other conditions such as diabetes mellitus or heart failure.
Merck Vet Manual: Disorders of the Adrenal Glands in Dogs
Clinical Anatomy & Physiology for Veterinary Technicians, Thomas Colville DVM, Joanna M. Bassert VMD, Mosby Inc. St Louis, MO, 2002