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Spay/Neuter? Here is a Whole Library of Studies Dr. Karen Becker Listed


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Dr. Kaen Becker put together a whole list of studies about Spay/Neuter
So do your research!

Dr. Karen Becker

Vets read the latest journal articles, and their clients are asking more questions about the timing of spay/neuter, wanting to engage in an honest discussion about long-term health consequences, and what hormone-preserving sterilization surgery options are offered.
The problem is, most of us don’t offer any surgical sterilization alternatives, like hysterectomy or vasectomy, because we didn’t learn how to do them in vet school. We didn’t learn how to vasectomize 8 week old shelter puppies, only castrate them. So that’s what we do. But science is showing this isn’t the best choice for longterm health.
We all agree that, other than rigorously healthy, genetically resilient dogs registered in DNA-diversifying breeding programs, all dogs should be sterilized. No one is arguing that. NO UNWANTED LITTERS OR UNHEALTHY PUPPIES!

But you can’t deny the research— I’ll post several dozen more studies in the comment section, along with a link to a recent FB live I did with a desexing expert/theriogenologist, who summarized the current research with this comment:
“Gonadectomized (neutered) dogs have been reported to have a higher incidence of obesity, urinary incontinence, urinary calculi, atopic dermatitis, autoimmune hemolytic anemia, hypoadrenocorticism, diabetes mellitus, hypothyroidism, immune-mediated thrombocytopenia, inflammatory bowel disease, hip dysplasia, cranial cruciate ligament rupture, aggressive and fearful behavior, cognitive dysfunction syndrome, prostate adenocarcinoma and transitional cell adenocarcinoma. Musculoskeletal issues may be especially significant for large breed dogs gonadectomized before they have finished growing, as bone physeal closure is delayed,”
Michelle Anne Kutzler, MBA, DVM, PhD, DACT, Professor of Theriogenology, Oregon State University.
And this latest paper: neutering appears to be a significant factor linked to hypothyroidism in dogs (paper link also in comments).
So where do we go from here? Please, vet schools around the world
: teach your students the simpler and easier hormone-preserving surgical techniques so vets can offer their clients options that achieve ALL goals: no unwanted litters AND the preservation of health and longevity. We CAN achieve both goals, but we need the help of veterinary schools, worldwide. The more we learn, and apply what we learn, the healthier our pups will be, but it takes a collective effort

Dr. Karen Becker

More reading on the subject:
Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (1AD, January 1). Assisting decision-making on age of neutering for 35 breeds of dogs: Associated Joint Disorders, cancers, and urinary incontinence. Frontiers. https://www.frontiersin.org/.../10.../fvets.2020.00388/full

Salt, C., Morris, P. J., Wilson, D., Lund, E. M., & German, A. J. (n.d.). Association between life span and body condition ... - wiley online library. https://onlinelibrary.wiley.com/doi/full/10.1111/jvim.15367

Zwida, K., & Kutzler, M. A. (n.d.). Non-reproductive long-term health complications ... - parsemus foundation. https://www.parsemus.org/.../03/Zwida-and-Kutzler-2016.pdf

Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (n.d.). Neutering of German shepherd dogs: Associated ... - wiley online library. https://onlinelibrary.wiley.com/doi/full/10.1002/vms3.34 ��

Hoffman, J. M., Creevy, K. E., & Promislow, D. E. L. (n.d.). Reproductive capability is associated with lifespan and cause of death in companion dogs. PLOS ONE. https://journals.plos.org/plosone/article... ��

Sanborn, L. J. (n.d.). Long-term health risks and benefits associated with ... - naiaonline.org. https://www.naiaonline.org/.../LongTermHealthEffectsOfSpa...

�Sundburg, C. R., Belanger, J. M., Bannasch, D. L., Famula, T. R., & Oberbauer, A. M. (2016, December
. Gonadectomy effects on the risk of immune disorders in the dog: A retrospective study - BMC veterinary research. BioMed Central. https://bmcvetres.biomedcentral.com/.../s12917-016-0911-5

�Bryan, J. N., Keeler, M. R., Henry, C. J., Bryan, M. E., Hahn, A. W., & Caldwell, C. W. (2007, May 21). A population study of neutering status as a risk factor for canine prostate cancer. https://onlinelibrary.wiley.com/doi/abs/10.1002/pros.20590

�Aaron, A., Eggleton, K., Power, C., & Holt, P. (1996, November 30). Urethral sphincter mechanism incompetence in male dogs: A retrospective analysis of 54 cases. The Veterinary record. https://pubmed.ncbi.nlm.nih.gov/8961524/

�Hagman, R. (1970, January 1). New aspects of canine pyometra. https://pub.epsilon.slu.se/736/

Allen, A. (2003, August). Tumors in domestic animals, 4th edition. The Canadian Veterinary Journal. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC340250/

Zink, M. C., Farhoody, P., Elser, S. E., Ruffini, L. D., Gibbons, T. A., & Rieger, R. H. (2014, February 1). Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized vizslas. AVMA. https://avmajournals.avma.org/.../244/3/javma.244.3.309.xml

Forsee, K. M., Davis, G. J., Mouat, E. E., Salmeri, K. R., & Bastian, R. P. (2013, April 1). Evaluation of the prevalence of urinary incontinence in spayed female dogs: 566 cases (2003–2008). AVMA. https://avmajournals.avma.org/.../242/7/javma.242.7.959.xml

Lefebvre, S. L., Yang, M., Wang, M., Elliott, D. A., Buff, P. R., & Lund, E. M. (2013, July 15). Effect of age at gonadectomy on the probability of dogs becoming overweight. AVMA. https://avmajournals.avma.org/.../243/2/javma.243.2.236.xml

Light, V. A., Montgomery, R. D., & Akingbemi, B. T. (2012, August 1). Sex hormone regulation of collagen concentrations in cranial cruciate ligaments of sexually immature male rabbits. AVMA. https://avmajournals.avma.org/.../73/8/ajvr.73.8.1186.xml

Howe, L. M., Slater, M. R., Boothe, H. W., Hobson, H. P., Holcom, J. L., & Spann, A. C. (2001, January 15). Long-term outcome of gonadectomy performed at an early age or traditional age in dogs. AVMA. https://avmajournals.avma.org/.../2/javma.2001.218.217.xml ��

Howe, L. M., Slater, M. R., Boothe, H. W., Hobson, H. P., Fossum, T. W., Spann, A. C., & Wilkie, W. S. (2000, December 1). Long-term outcome of gonadectomy performed at an early age or traditional age in cats. AVMA. https://avmajournals.avma.org/.../11/javma.2000.217.1661.xml

LM, H. (1997, July 1). Short-term results and complications of prepubertal gonadectomy in cats and dogs. Journal of the American Veterinary Medical Association. https://pubmed.ncbi.nlm.nih.gov/9215412/

Assisting Decision-Making on Age of Neutering for 35 Breeds of Dogs: Associated Joint Disorders, Cancers, and Urinary Incontinence

Assisting Decision-Making on Age of Neutering for 35 Breeds of Dogs: Associated Joint Disorders, Cancers, and Urinary Incontinence

Dr. Karen Becker

KR., S., MS., B., SL., S., & V., S. (1991, April 1). Gonadectomy in immature dogs: Effects on skeletal, physical, and behavioral development. Journal of the American Veterinary Medical Association. https://pubmed.ncbi.nlm.nih.gov/2045340/

�Farhoody, P., & Zink , C. M. (2010, May). Behavioral and Physical Effects of Spaying and Neutering Domestic Dogs (Canis familiaris). http://www.atftc.com/health/SNBehaviorBoneDataSnapShot.pdf

�Cooley, D. M., Beranek, B. C., Schlittler, D. L., Glickman, N. W., Glickman, L. T., & Waters, D. J. (2002, November 1). Endogenous gonadal hormone exposure and bone sarcoma risk1. American Association for Cancer Research. https://aacrjournals.org/.../Endogenous-Gonadal-Hormone...

Riva, G. T. de la, Hart, B. L., Farver, T. B., Oberbauer, A. M., Messam, L. L. M. V., Willits, N., & Hart, L. A. (2013, February 13). Neutering dogs: Effects on joint disorders and cancers in Golden Retrievers. PLOS ONE. https://journals.plos.org/plosone/article... ��

Kim, H. H., Yeon, S. C., Houpt, K. A., Lee, H. C., Chang, H. H., & Lee, H. J. (2005, May 4). Effects of ovariohysterectomy on reactivity in German shepherd dogs. The Veterinary Journal. https://www.sciencedirect.com/.../abs/pii/S109002330500064X

Hart, B. L., Hart, L. A., Thigpen, A. P., & Willits, N. H. (2014, July 14). Long-term health effects of neutering dogs: Comparison of labrador retrievers with golden retrievers. PLOS ONE. https://journals.plos.org/plosone/article... ��

BL, H. (2001, July). Effect of gonadectomy on subsequent development of age-related cognitive impairment in dogs. Journal of the American Veterinary Medical Association. https://pubmed.ncbi.nlm.nih.gov/11439769/ ��

W, B., JM, C., & DC, B. (2012). The effect of neutering on the risk of mammary tumours in dogs--a systematic review. The Journal of small animal practice. https://pubmed.ncbi.nlm.nih.gov/22647210/ ��

Brodey, R.S., Goldschmidt, M.A., Roszel, J.R. (1983). Canine mammary gland neoplasms. Journal of American Animal Hospital Association, 19:61-90
Katherine Salmeri, DVM, Mark Bllomber, DVM, Sherry Scuggs, BS, Victor Shille DVM, Journal of American Vet Med Association, Volume 198, No 7 1991
Meuten, D.J. (2002). Tumors in Domestic Animals. 4th Edn. Iowa State Press, Blackwell Publishing Company, Ames, Iowa, p. 575��

Stubbs, P. and Bloomberg, M. (1995). Seminars in Vet Med & Surgery, Small Animal, Volume 10, No 1 Feb 1995 Dept of Small Animal Clin Sci, Univ of Florida��

Michael DeTora, Robert J. McCarthy. (2011) Ovariohysterectomy versus ovariectomy for elective sterilization of female dogs and cats: is removal of the uterus necessary?. Journal of the American Veterinary Medical Association 239:11, 1409-1412.

Margaret V. Root Kustritz. (2007) Determining the optimal age for gonadectomy of dogs and cats. Journal of the American Veterinary Medical Association 231:11, 1665-1675.

Online publication date: 4-Dec-2007.
Citation | Full Text
Felix M. Duerr, Colleen G. Duncan, Roman S. Savicky, Richard D. Park, Erick L. Egger, Ross H. Palmer. (2007) Risk factors for excessive tibial plateau angle in large-breed dogs with cranial cruciate ligament disease. Journal of the American Veterinary Medical Association 231:11, 1688-1691.
Online publication date: 4-Dec-2007.

Abstract | Full Text
Fuess, Theresa A., PhD, VM-3. Early-Age Spay/Neuter: An Overview. Illinois Veterinary Bulletin, Spring, 1998. http://vetmed.illinois.edu/ope/ivb/spay-neu.htm

Mackie, Marvin, DVM. Early Age Neutering: Perfect for Every Practice. Paws to Think, Autumn 2002, Vol 1, Issue 3.

Spain, C. Victor, DVM PhD; Scarlett, Janet M. DVM PhD; Houpt, Katherine A. VMD, PhD, DACVB (2002, Febuary 1). Long-term risks and benefits of early age gonadectomy in cats. JAVMA. http://avmajournals.avma.org/.../javma.2004.224.380...

Spain, C. V., Scarlett, J. M., & Houpt, K. A. (2004, February 1). Long-term risks and benefits of early-age gonadectomy in dogs. AVMA. https://avmajournals.avma.org/.../3/javma.2004.224.380.xml

Rottweiler study links ovaries with exceptional longevity

Dog Neutering is an Emotive Subject for Welfare and Population Reasons but let’s take a look at the Facts… https://dogsfirst.ie/health-issues/dog-neutering/
Gonadectomy in Dogs: Considerations & Review

Kislak, Paula, DVM. Early Age Spay/Neuter.

Hormone-Sparing Sterilization

Restoring hormone levels in a neutered dog leads to health improvements

Spay/Neuter And Joint Disease

Spaying and Castration (Neutering) Dogs https://www.doglistener.co.uk/spaying_neutering-shtml

Your Dog Needs To Be Spayed Or Neutered – Right?

Why I’ve had a Change of Heart About Neutering Pets

Sterilization Effects Worse for Golden Retrievers Than Labs

Neutering: This Common Procedure Can Boost Cancer and Joint Problems As Much As Five-Fold

Illegal in Scandinavia, Surgical Sterilization Is Still Routine in America

Risks and Benefits to Spaying/Neutering Your Dog

Gonadectomy in immature dogs: effects on skeletal, physical, and behavioral development - PubMed

Gonadectomy in immature dogs: effects on skeletal, physical, and behavioral development - PubMed


Understanding the effects of sustained supraphysiologic concentrations of luteinizing hormone in gonadectomized dogs: What we know and what we still need to learn​

Author links open overlay panelMichelle AnneKutzlerDepartment of Animal and Rangeland Sciences, Oregon State University, 112 Withycombe Hall, Corvallis, OR, 97331, USA
Received 29 June 2022, Accepted 4 November 2022, Available online 9 November 2022, Version of Record 29 November 2022.

Part of an email I received from Dr. Becker

Finally: Experts look at neutering risks​


Hey, I'm telling you, it's time to rethink this!​
When you’ve got a newbie in your pack or pride, the subject of neutering is likely on your mind as they grow and come into sexual maturity.

I wrote about the risks of considering neutering “routine” some years back, as the data was piling up showing cancer and other diseases significantly more likely in the neutered pet.

Imagine my joy when I saw a main stream, credentialed vet, calling out “when and IF” neutering should take place.

Those are heartening words, from the article in very main stream online journal called Clinician’s Brief, by Karen M. Tobias, DVM, MS, DACVS, University of Tennessee.

The latter abbrev stands for Diplomate of the American College of Vet Surgeons (you know, the knife wielders, whose motto typically is “A chance to cut is a chance to cure!”).

You have to be a bit crafty if you want to read the full article (like name your university as you set up a free account when you click through), but I’ll share the highlights for you here.

More vet eyeballs, Yeah!​

The fact that a main stream vet is publishing something under the heading of “Spaying & Neutering in Dogs: Benefits & Risks” is encouraging.

It means the concerns I pointed out years ago are reaching more veterinary eyeballs.

Will Dr. WhiteCoat read it and slow down his spaying agenda?

That’s a big maybe.

As the author points out, it’s very a common procedure, and more easily done in the young (who have the greatest risks for bad outcomes, as the research has pointed out for a decade or so).

Benefits of neutering? Meh.​

The author paints a picture of benefits of neutering in avoiding certain diseases I don’t agree with.


The wild cousins (read: intact wolves, coyotes, dingos, etc.) don’t suffer the same diseases that intact pets do, for the following reasons.

Most pets…

  • are heavily vaccinated, far too many annually (immediate cause to FIRE your vet)
  • often pesticide laden (Fleas! Ticks! Heartworm! Kill ‘em all with this shot or pill before disaster strikes!)
  • and poorly fed (here’s looking at you, Science Diet and all you kibble makers)
The diseases she names that would be unlikely to show in Vital Animals, aka Naturally Reared animals include:

A. Testicular, ovarian or uterine cancers

B. Pyometra

C. Prostate hyperplasia, uterine polyps

D. Maybe even diabetes! (Another man-made disease, of course, which no wild cousins would even come close to getting. Are you with me? Diabetic wolf? Not happening.)

Lies, Damned Lies, and Statistics​

As a boarded surgeon, this doc knows how to read and properly interpret statistics, which most vets, myself included, have never gotten agile at.

What’s most encouraging in this instance, is Dr. Tobias takes on the myth of “mammary cancer’s gonna get your bitch if you leave her intact!”

Her words that brought a smile to my face:

Gonadectomy before sexual maturity reportedly reduces the overall risk for mammary tumor development; however, a systematic review found moderate to high risk for bias in published canine studies.

Not good in the world of science, right?

That’s what makes the sellers of the latest vaccines unfair judges of those vaccines’ safety (looking at you, Moderna, Pfizer, et al).

She goes into detail about how minuscule that risk really is, from the often misquoted and misinterpreted study she cites.

The truth of that study, when a statistician looks at “relative risk” of keeping your female intact breaks down like so:

The estimated annual incidence of mammary cancer occurring in 100,000 intact dogs is:

  • 0.18%— (184 out of 100,000 dogs)
Even waiting before you spay is a low risk, according to the actual data.

  • If you spay before the first heat (ugh, please don’t), your risk of mammary cancer is near zero: 0.001%
  • If you wait until before the 2nd heat, it’s 0.015%
  • And, if you wait to spay until before the 3rd heat, it’s still only 0.048%!
That means about 5 dogs in 1000 may get the mammary tumors!

And you can reduce those odds even further by raising your animals to be Vital Animals!

She’s using stats from the conventional medicine consuming pets.

The article calls out certain breeds more at risk, but again: raise those breeds naturally, and your risk is likely minimized.

Pyometra: the other spectre of the un-neutered?​

Dr. Tobias says the overall risk of uterine infection, aka pyometra, in unspayed females is about 19% by 10 years of age, with some breeds (Bernese mountain dogs, Bouvier des Flandres, bull terriers, Irish wolfhounds, keeshonds, Leonbergers, Newfoundlands, rottweilers, and Staffordshire bull terriers) at or exceeding 50%.

Again: these data are skewed towards those conventionally raised dogs.

If you choose the path of risky “prevention” sold by the big box vet clinics, yes, you’d better spay your female, probably by four years of age.

But, following the natural path, again, your risk is greatly diminished.

And, I can tell you from homeopathic practice experience, pyometra can be cured by a competent homeopathic vet without surgery.

She shares the well known research I cited in my article on the increased risks of neutering causing:

  • Joint disease
  • Urinary incontinence
  • Other cancers, perhaps
  • And one I missed: obesity!
Obesity is more likely in the “gonadectomized” (the surgeons’ $40 word for spayed or castrated, both of which are covered by the term “neutered.”)

But again: kibble makes obesity far more likely. Carbs, my friends, are species agnostic.

We agree on some things​

Mainly, the point I counseled my clients on for years has always been:

IF you choose to neuter, at least wait until maturity has set in. That means growth has ceased and the urethral sphincter is fully functional.
In short, the convenience to Dr. WhiteCoat to neuter early is not in your pet’s best interests.

She doesn’t point out how Americans hold neutering as “more responsible” and equate it's absence as the sole cause of pet overpopulation.

I do in my article. Other countries who neuter far less than we do are not seeing gross overpopulation and all its complications.

In the end, this is an individual decision you must make, and it’s not a small one.

Be wise, study neutering’s ramifications vs those of leaving your pet intact, and decide based on facts rather than emotions.

Groundbreaking Study Released on Sterilization Alternatives​

Analysis by Dr. Karen Shaw Becker

May 8, 2023
Do traditional spay and neuter surgeries increase the risk for disease, including malignancy? Are there better alternatives? This just-published, first-of-its-kind study involving over 6,000 dog owners documents the truth about what I've suspected and observed for years.


  • Studies show that spaying/neutering dogs increases the risk for many diseases, including several types of cancer, along with behavioral problems
  • Unfortunately, sterilization techniques that preserve the ovaries or testes and the important hormones they produce are not taught in veterinary schools; there has also been very little research on the benefits vs. drawbacks of these procedures
  • However, a just-published, first of its kind study involving over 6,000 dog owners reveals that spayed/neutered dogs develop more health and behavioral problems than intact dogs and dogs who underwent gonad-sparing sterilization procedures
  • These study results suggest that the bodies and brains of dogs benefit from maximum exposure to the sex hormones; the researchers concluded that "dogs might benefit from these alternative surgeries, with respect to general health and experience better behavior outcomes, compared to undergoing traditional spay-neuter surgery”