Health and Happiness: the Canine-Human Connection

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Billy – Healthy & Happy

Many of the advances in human healthcare and science can be attributed to the fact that we are able to try various medical treatments on our canine best friends before applying them to humans. This is because, from a physiological and biological perspective, humans and canines are very similar. In  fact, we routinely utilize canine models in human medical research (e.g., cardiovascular studies, cancer, heart and lung research, orthopedics, neurology).

Does it make any sense then, that you would take a procedure you know to be extremely harmful to humans (and in some cases illegal) and mandate that it be performed on each and every dog – with almost NO exception and without the benefit of any peer- reviewed research establishing its safety?  And, taking it a quantum leap further, would you then promote this procedure as actually being good for dogs? The quintessential example of this would have to be the spay (ovariohysterectomy) of female dogs and the neuter (castration) of male dogs (please see the section “The Smoking Gun”  for a simplified explanation from an expert). Contrast these overly invasive and often unsafe sterilization procedures with those we safely perform on humans, i.e., tubal ligations on females and vasectomies on males. This begs the question, why can’t vasectomies and tubal ligations be performed on our canine best friends? The short answer is, “They can!”. According to a 2007 systematic review 83 of more than 50 peer reviewed studies regarding the effects of spay/neuter:

“One thing is clear – much of the spay/neuter information that is available to the public is unbalanced and contains claims that are exaggerated or unsupported by evidence. Rather than helping to educate pet owners, much of it has contributed to common misunderstandings about the health risks and benefits associated of spay/neuter in dogs.”

Spay and neuter are also promoted as providing a solution to canine behavioral problems (e.g., aggression, fear and anxiety, excitability) in female and male dogs. However, as observed by Dr. Stanley Coren in Psychology Today, the latest peer-reviewed studies show that contrary to conventional wisdom, spaying/neutering was associated with significantly worse behavior.  Please see sections Behavioral Effects of Spay  and Behavioral Effects of Neuter  for a full discussion of the current studies regarding spay/neuter and canine behavior.

Another oft-repeated aspect of spay/neuter that we must challenge is the assertion that spay/neuter lengthens the lives of our dogs. On our Lifespan page, we discredit a recent study supporting spay/neuter as a procedure which will enhance the lifespan of the family dog. We also introduce studies which conclude that ovarian hormones in females lay the foundation for adult health outcomes, including longevity. Further, we are able to introduce studies which demonstrate the hormonal imbalance brought on by spay/neuter negatively affects the dog’s ability to respond to stress. This inability to respond to stress creates changes in the dog consistent with accelerated aging and consequently shortens the lifespan of spayed/neutered canines.

With respect to spay (ovariohysterectomy) of female dogs, both the uterus and ovaries are removed to achieve sterilization, with no consideration for hormone replacement. Spay is also often recommended to avoid life-threatening pyometra. However, the spay surgery itself is a complex, highly invasive procedure. It is rarely explained to dog guardians prior to the spay procedure that spay  itself can have serious complications such as stump pyometra, ovarian remnant syndrome, and uterine stump granuloma (see our “Complications of Spay” section for more detail). Add to this the lifelong effects of hormonal disruption, and it becomes clear spay is not a decision to be taken lightly or a procedure that should be “standard operating procedure”. We will utilize current studies/data throughout this website to illustrate spay’s negative medical and behavioral ramifications for healthy female dogs. In healthy human females, if sterilization is desired, we perform tubal ligation. This is much less invasive without the potential complications of spay. Because tubal ligation leaves the ovaries and uterus intact, hormone balance is preserved. Hysterectomy or ovariohysterectomy is performed on humans when there is a medical necessity to remove the uterus/ovaries due to disease. In that circumstance, hormone replacement therapy is typically a part of the post-surgical protocol.

With respect to neuter (castration), there is long term evidence regarding the medical ramifications for healthy young human males in previous societies dating back several centuries. The historical information is consistent with data/conclusions from current studies of castration. Due to the long-term medical consequences, we now opt for vasectomy in human males, so as to preserve the testes and the hormones they produce. Surgical castration of human males remains highly controversial, if not illegal, even when performed on convicted sexual predators. A review 81 of the literature on the subject of castration with respect to its medical consequences in previous societies concludes:

“Hopefully, it will never again be possible to repeat the studies reviewed in this paper, as in more recent times we have used different means of expressing man’s inhumanity to man.”

The ACLU argues surgical or chemical castration 82 of humans is considered “cruel and unusual punishment”. Why would we inflict this upon our innocent dogs without a second thought?

Billy  (effects of neuter over time)

After spending 13 years battling behavioral and physical problems with our dog Billy, we finally came to the devastating conclusion that all of his suffering was the result of his being neutered as a young dog in a shelter. Once we came to that conclusion, we uncovered a wealth of information/research that supported our position. We were left wondering why no one in the veterinary community ever revealed to us that this was all quite predictable based solely on Billy’s being neutered at a young age.


Hormones are substances secreted by glands throughout your body (a complete discussion of hormones can be found on the page, “Hormones and the Endocrine System“). Hormones regulate everything from hunger to reproduction and influence nearly every cell, organ, and metabolic function. Together, hormones and glands make up the endocrine system. For people (or dogs) to stay healthy, hormones must be released in the right amounts, and glands must be able to adjust the release of hormones in response to a changing environment.

Removal of the ovaries and testes disrupts the production of sex hormones (i.e., testosterone, estradiol, progesterone), which, by definition, makes spay/neuter an endocrine disruptor (ED). According to the Endocrine Society’s latest Scientific Statement on the subject of EDs, the loss/reduction of sex hormones is not inconsequential:

“…levels of any hormone must be within a physiologically relevant range to be most effective. Excursions outside of that range to superphysiological (elevated) or subphysiological (depressed) levels for any extended period nearly always result in dysfunction or disease.” 176

Studies have shown the endocrine disruption caused by spay or neuter often leads to a weakened immune system, altered metabolism, chronic disorders/disease, and behavior problems. However, veterinary schools and many veterinary organizations still insist spay or neuter is healthful for dogs and should be the standard procedures to prevent dog overpopulation. This is in direct contrast to the entire thesis of the “Canine-Human Connection”.


There are a group of chemicals, both natural and man-made, that exist in our environment and are also endocrine disruptors (EDs) or endocrine disrupting chemicals (EDCs).  The hormones primarily affected by these chemicals are the same sex hormones affected  by spay/neuter. These EDCs include a spectrum of substances that can be loosely classified according to their known or suspected activity in relation to sex hormone receptors and pathways,  generally mimicking or blocking male and female sex hormones. The names of some of these EDs might be familiar to you and include DDT, dioxin, BPA, PFOA, atrazine (herbicide), PCBs, and arsenic. These endocrine disrupting chemicals have been studied extensively in humans and wildlife, and to our knowledge, there are no studies asserting the benefits of exposure to these chemicals.

In males, for example, DDT is one ED known to “chemically castrate 70 (i.e., neuter) its victims. Broadly speaking, the effects on humans of exposure to identified EDs is quite similar to the effects of spay/neuter on our young dogs. We will explore this in depth in the Diseases section of this website, where we will refer you to resources from the Hormone Health Network. The Hormone Health Network is the public education affiliate of the 100 year old Endocrine Society – the largest global membership organization representing professionals (medical doctors, scientists, researchers, and educators) from the field of endocrinology.

At a recent European Union (EU) conference on endocrine disruptors,65 R. Thomas Zoeller, PhD, an invited spokesperson for the Endocrine Society, stated:

“It’s important for regulating agencies to understand that hormones control elements of development that are irreversible when disrupted. We are facing a continuing pandemic of chronic disease if we do not act now.”

Spay/neuter is the ultimate ED, and it is never a responsible option for a young, healthy dog. Yes, we said NEVER. The conclusions of Dr. Zoeller (just above), with respect to endocrine disruptors are remarkably similar to the conclusions in a 2013 UC Davis study of the effects of spay/neuter:

“Because [spaying and] neutering can be expected to disrupt the normal physiologic developmental role of gonadal [i.e., sex] hormones on multiple organ systems, one can envision disease syndromes…” 

Once a dog has been spayed or neutered, their endocrine system has been forever altered. There is no going back to optimal health, despite best efforts. In fact, we will illustrate on our Diseases Overview and the Stress Response System pages of this website how spay/neuter permanently damages your dog’s ability to respond to physical and/or psychological stress; leaving your dog increasingly susceptible to cancer, metabolic disease including diabetes, immune-related disease, infection and anxiety. The damage of spay/neuter to the endocrine system of your dog is permanent, and no dog is immune.

We will summarize the multitude of studies revealing the consequences of spay/neuter in the Spay and Neuter sections of this website (note: there are over 190 peer reviewed studies referenced in our Bibliography). We will document the developmental damage of early spay/neuter in the Orthopedic section and the emerging chronic diseases related to spay/neuter in the Hormones and the Endocrine System section of this website. The Research section explains why it is acceptable to apply the research and studies pertaining to endocrine diseases in humans as a basis for understanding the emerging disease entities in dogs. In our History section, we will discuss at great length how our dog Billy’s health problems led us to our conclusions.

In short, spay/neuter significantly increases the risk of an otherwise young, healthy dog developing:

  1. Orthopedic problems
    • hip dysplasia
    • elbow dysplasia
    • CCL ligament tear in their knees (requires TPLO surgery)
  2. Cancer
    • osteosarcoma
    • hemangiosarcoma
    • Lymphosarcoma
    • mast cell tumor
  3. Diseases of the endocrine (hormone) systems
    • hypothyroidism
    • Cushings and Atypical Cushings
    • Type 2 diabetes
    • Hyperestrinism and Alopecia (hair loss)
    • Allergies (atopic dermatitis)
    • Obesity
  4. Behavior problems
    • aggression towards people and other dogs
    • fear and anxiety
    • reactivity to touch or handling
Spay/Neuter – the ultimate endocrine disruptor

Spay/neuter, the ultimate endocrine disruptor, is the key to the increase of all of the seemingly unrelated detrimental conditions our dogs suffer from as documented throughout this site. We recognize spay/neuter is a means to an admirable goal. However, is it ethical to compromise the right to a healthy and happy life for the individual dog for the perceived “greater good” of controlling dog overpopulation?  A 2012 Texas A&M research paper 99  titled, “Inconvenient Desires: Should We Routinely Neuter Companion Animals?”, explores this very question. Summarizing their conclusions:

Routine neutering of companion animals raises significant ethical questions and from some ethical perspectives, looks highly problematic. In the case of male dogs and the long-term health risks involved, routine neutering is not morally justified.

We don’t believe any dog should be condemned to a life of pain and illness when viable alternatives which protect your dog’s hormones exist. We would strongly recommend the time and human tested procedures of tubal ligation and vasectomy as safe and ethical alternatives to conventional spay/neuter for our dogs. This solution also prevents pet overpopulation.

According to a 2001 published UC Davis Behavior Service study 55 :

“There may be a need to evaluate possible methods for counteracting the effects of loss of sex hormones in gonadectomized [i.e., having had ovaries or testes surgically removed] dogs.” (Dr. Benjamin Hart;  School of  Veterinary Medicine, UC Davis; J Am Vet Med Assoc 2001; 219:51–56)

Further, in 2013 60 and 2014,61 UC Davis published studies linking spay/neuter to three significant orthopedic problems and four aggressive cancers in Golden Retrievers, Labrador Retrievers and German Shepherds. In July of 2020, the research team at UC Davis followed up with studies from the same database to look at the aforementioned orthopedic problems and cancers among 35 other dog breeds as well as mixed breed dogs. The breed-specific results were intended to reveal the range of differences in disease vulnerability to spay/neuter. The researchers provide advice regarding the timing of spay/neuter to minimize these orthopedic problems and cancers within specific breeds.180 Among mixed breed dogs the major differences in vulnerability seemed to be based upon size, with dogs under 43 lbs. showing less vulnerability to the cancers and orthopedic problems specific to these studies.181 The authors point out that these studies do not take into consideration other adverse outcomes (e.g. accelerated brain aging, cognitive decline, behavioral changes) with documented association to hormone deficiencies as a result of spay/neuter. The other limitation we see with these studies is that the median age of the dogs’ last visit was 4.9 to 6.0 years old. Generally the diagnosis of the cancers in question, and often the orthopedic issues occur when the dog is older than this age range. In that circumstance, the study will not be able to record that diagnosis, and this makes the conclusions of this study less reliable.

The UC Davis studies were intended to serve a practical purpose because in their home state of California all shelter dogs are required by law to be spayed or neutered prior to adoption. Additionally, many dogs purchased from breeders are either spayed/neutered prior to release of the dog or sold with a requirement for spay/neuter at a later date. In the situation of adoption from a breeder, the information in this study may be helpful, however people adopting shelter dogs will have no input as to when the dog will be spayed or neutered. In an April 2013 interview with one of the principals for this study, Dr. Benjamin Hart (see our “Smoking Gun” page), points out that tubal ligation and vasectomy would control canine overpopulation without the increased prevalence of deadly cancers and orthopedic deformities. Why is it, then, that this information was not included in any of these published studies? Why does UC Davis’ clinical program fail to promote or teach tubal ligation or vasectomy?

Unfortunately, UC Davis is not the only veterinary institution failing to teach or even discuss tubal ligation or vasectomy as safer and equally effective alternatives to spay/neuter. These UC Davis studies are particularly relevant because veterinary programs continue to debate the timing of spay/neuter as a means to deal with some of the unintended consequences these and many other studies have revealed.108

Several veterinarians, on the condition their names be withheld, confided  their belief that the financial windfall spay and neuter create for the veterinary industry has trumped the medical concerns of the affected dog (this becomes evident in our “Hidden Costs of Spay/Neuter” page). Consequently, it appears that change will only occur as a response to pressure from pet guardians. In fact, the authors of a study109 evaluating the risks of spay/neuter upon Vizslas, direct their peers to discuss the harmful effects of spay/neuter with their canine guardians as part of the requisite “informed consent” process. In order to ensure you get the necessary information to make a good decision regarding your dog’s care, it would be appropriate for you to introduce/reacquaint your veterinarian to a concept known in human medicine as “shared decision making63 (SDM).  Sharing decisions by way of providing information, as opposed to clinicians making decisions on behalf of patients, is gaining increasing prominence in health care policy. SDM has been defined as:

“…an approach where clinicians and patients share the best available evidence when faced with the task of making decisions, and where patients are supported to consider options, to achieve informed preferences”.

Pet guardians should be apprised of the option of tubal ligation/vasectomy with the understanding the pet guardian will need to exercise some judgment/restraint of both male and female dogs when a female dog is in heat.

Pressure from pet guardians to move from spay/neuter to tubal ligation/vasectomy is being fueled by breed-specific organizations who are studying the effects of spay/neuter upon their particular breed. One example of this is the Morris Animal Foundation Golden Retriever Study, which was undertaken due to the high incidence of cancer, obesity and orthopedic conditions exhibited specifically in Golden Retrievers. Although they are studying genetics, environment, diet and many factors affecting the incidence of these conditions, early results are pointing directly to spay/neuter as a major culprit for the increased incidence of all three.

If a significant number of pet guardians demand tubal ligation and vasectomy as a method of population control, the veterinary surgeons will respond accordingly and educate themselves on the intricacies of these surgical procedures. We are told by experts in the field that these procedures are simpler (from a technical perspective), have fewer complications and should ultimately be less costly. This should appeal to shelter managers and other custodians of the bottom line as well. If you have difficulty locating a veterinarian in your area who is capable and willing to perform hormone sparing sterilization alternatives to traditional spay/neuter (e.g., vasectomy, tubal ligation, ovary-sparing spay), we recommend that you refer to our Frequently Asked Questions (FAQ) or our Facebook page.

Should the veterinary community get on board with our recommendations with respect to hormone sparing sterilization alternatives to traditional spay/neuter, any laws requiring spay/neuter can easily be amended to require “sterilization”. This would not preclude spay or neuter if that was desired, but also allow tubal ligation and vasectomy as legally valid options for shelter dogs. We would also be positioned to take advantage of new procedures to prevent reproduction that technology may bring us in the future. Please visit our Legal section for information regarding each state’s law and a detailed discussion on how to change your state law if necessary.

We are making progress! If you visit our Legal section you will see that in 2016, both the American Veterinary Medical Association (AVMA) and the American Society for the Prevention of Cruelty to Animals  (ASPCA) only recognized/recommended spay/neuter as legitimate methods of preventing pet overpopulation. Today, however, the AVMA recognizes other hormone-sparing procedures specifically, and the ASPCA recommends “sterilization” which would also allow for hormone-sparing procedures as we are advocating.


If your current dog has already been spayed/neutered, the damage has most likely already been done to a large extent. We will do our best to advise you of offsetting measures that were somewhat successful for our dog and/or that we discovered in our research. We ask that you please work with us to change the status quo for all pets – present and future.

This website is dedicated to Billy.

Disclaimer:   Healthy and Happy Dog is intended to provide information helpful to dog guardians, and hopefully veterinarians, as a public service. We do not accept any advertising nor do we promote any products or services.