How Do Your Dog’s Hormones Affect Their Health and Behavior?

From estrogen and testosterone to adrenaline and cortisol, your dog’s hormones have a profound impact on their well-being — physically, mentally and emotionally.

Most people know that hormones are important for regulating body systems. These natural chemicals impact systems and metabolism on almost every level of the body, and also have a significant influence on behavior and mood — not only in ourselves, but in our dogs as well. Read on for a discussion of the most common hormones and how they affect your dog’s health and behavior.


A hormone is a chemical transmitter substance produced by cells in the body. It is transported through the bloodstream to the cells and organs on which it has a specific regulatory effect. In other words, hormones act as chemical messengers within the body, in order to stimulate or suppress certain processes or actions.


There are dozens and dozens of different hormones in the body, but the most well-recognized players include:

  • Testosterone
  • Estrogen
  • Adrenaline
  • Cortisol
  • Thyroid hormone
  • Growth hormone
  • Insulin
  • Melatonin

Additionally, specific neurotransmitters act as hormones in the body, and these include serotonin, dopamine, and GABA.

All these hormones act within complex networks collectively referred to as the endocrine system. The endocrine system is a network of glandular organs that produce and regulate hormones to control and coordinate the body’s metabolism, energy level, reproduction, growth and development, response to injury and/or stress, and mood.

Crucially important glands within the endocrine system include:

  • Hypothalamus
  • Pineal gland
  • Pituitary gland
  • Thyroid gland
  • Parathyroid gland
  • Thymus
  • Adrenal gland
  • Pancreas
  • Ovaries
  • Testes

The gut (gastrointestinal tract) also acts as an endocrine gland since it works with endocrine cells, neurons, and immune cells, using gut peptides as signaling substances. In fact, some of the hormones in the gut are also found in the brain, which supports the concept of the gut-brain axis.


These health problems are very common in our canine companions, and appear to be on the rise. There are many reasons for this, such as:

  1. Processed foods and toxins: Many toxins are known to be direct endocrine disruptors, and include common pet food preservatives such BPA and BHA, and herbicides in foods such as glyphosate (Roundup).
  2. Nutrient deficiencies: Trace minerals such as magnesium, selenium, zinc, potassium and iodine are critically important for the body’s glands to function appropriately. Trace mineral deficiencies are very common in both dogs and humans.
  3. Spaying and neutering: Typically, when pets are de-sexed, the gonads (ovaries or testicles) are completely removed, which means the majority of testosterone and estrogen are gone for good. It is important to note that a certain level of sex hormones is crucially important for sustaining normal health and well-being.

As it turns out, the only other glands in the body that can produce some sex hormones are the adrenal glands. This means the adrenal glands in a spayed or neutered dog are placed under extra stress and demand throughout the animal’s lifetime. The adrenal glands are also responsible for regulating and releasing adrenaline and cortisol hormones, which is in itself a big job. Adrenaline is the hormone released during the body’s fight or flight response, triggered when stressful events occur.

Cortisol is also released by the adrenals in fight or flight scenarios, and is continually released in chronic stress situations. Ongoing stressors for dogs can include things like chronic pain, chronic itching due to allergies, environmental stressors, household upsets, separation anxiety, etc.


Chronic anxiety is becoming more common in animals, with growing numbers of dogs being placed on prescription medications to manage it. The common metabolic causes of anxiety include HPA dysfunction, compromised gut health, and nutrient deficiencies.

  • The HPA axis describes the hypothalamic-pituitary-adrenal system, which is known as the command center and communication feedback system in the part of the brain that senses stress. The HPA axis controls reactions to stress and regulates digestion and the immune system, as well as mood and emotions.
  • When this system is continually firing under conditions of chronic stress, the negative feedback loop mechanism (which normally keeps things in check) can break down. This HPA dysfunction is recognized as a cause of chronic anxiety.
  • If the situation continues, this dysfunction can lead to adrenal gland depletion, otherwise known as adrenal fatigue. Other health conditions associated with adrenal dysfunction include Cushing’s and Addison’s diseases. All these adrenal gland conditions can affect a dog’s behavior, causing everything from anxiety and restlessness to low energy and fatigue.


If your dog is still sexually intact, they will have higher levels of sex hormones — i.e. testosterone in males and estrogen and progesterone in females. These can certainly also affect behavior and mood.

  • Testosterone is known to influence confidence, dominance, and potentially aggression. However, this is not to say a neutered dog won’t display these behaviors. In fact, some dog parents see their dogs’ aggressive or reactive behaviors actually heighten after neutering; it appears that, in some circumstances, removing the confidence-supporting testosterone hormone could lead to more fear-related aggression behaviors. This demonstrates that hormones have very complex effects on the body, mind and mood.
  • Estrogen is known to help regulate mood. In human women, low levels of estrogen are shown to influence anxiety, depression and stress.
  • Progesterone is a “feel good” hormone that has a calming effect. In female dogs, progesterone is released after ovulation during the heat cycle, whether they are bred or not (even if they do not become pregnant), and continues to be measured at high levels for many weeks after.

In conclusion, it’s clear that hormones exert vast effects on the body and directly influence the emotional and mental well-being of our dogs and ourselves.

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