Is Your Dog's Health at Risk? The Surprising Truth about Spaying and Neutering

PART TWO: Interview With Top Expert
Dr. Michelle Kutzler DVM, PhD, DACT

Since the spring, I have been sending you regular updates on my dog Pax's hormone replacement therapy and the remarkable changes I have seen.

For those of you who have missed the previous info, Pax had been suffering from repeated injuries and an ongoing shifting lameness for two years. 

The most shocking part is that his condition was a result of hormonal changes after he got neutered.

During more than 30 years as a veterinarian, I have neutered and spayed countless animals without knowing I was causing harm.

But now, when we understand the link between spaying, neutering, and a multitude of different health issues, from injuries, ligament tears, hypothyroidism, and cancer,  I decided to sound the alarm together with a few other colleagues. 

The good news is that we can still prevent unwanted pregnancies by what we call "hormone-sparing sterilization," vasectomy, and ovary-sparing spay, and prevent lifelong health problems related to conventional surgery.

Today, I would like to share a second interview with Dr. Michelle Kutzler, a veterinarian and reproductive specialist who is the top researcher in the field. 

You will learn why she started this research, what conditions she found related to spay and neutering, and what we can do about it.  I also share multiple links directly to the studies.

As I said, I am thrilled Pax is doing better, but millions of dogs need to be helped and protected, and together, we can change that!

Neutered and Spayed Dogs Suffer from Higher Rates of Hypothyroidism, Ligament Tears, Fear and Aggression Issues

An interview with a researcher, veterinarian and reproductive specialist:  Dr. Michelle Kutzler, DVM, PhD, DACT

Dr. Dobias: Michelle, I'm so happy to have you here for the second time.

Dr. Kutzler: Thank you again for this opportunity.

Dr. Dobias: There's so much to discuss; my head is bursting with thoughts and questions. Let's start. Maybe, if it's okay, I'll rehash what we said last time.

The Story Behind This Groundbreaking Research

Dr. Dobias: Many years back, your husband's family's Rottweilers kept getting sick and developing cancer, and it made you wonder if there was a connection with them being spayed and neutered. That's how your research started.

You realized there was a severe increase in luteinizing hormone (LH) in spayed and neutered dogs because the gonads were gone. This hormone attaches to receptors elsewhere in tissues, leading to inflammation, cancer, and other problems.

You've proven this in your research studies and have been trying to teach veterinarians about hormone-sparing sterilization, which keeps the gonads while preventing unwanted pregnancies.

Last time, you mentioned how difficult it was to convince the veterinary community to change their mindset and adopt these safer procedures.

Dr. Kutzler: Yes, that's correct.

Dr. Dobias: It's overwhelming to think of all the different conditions I've seen over the past 30-plus years: inflammatory conditions, joint issues, cruciate ligament problems, skin issues, allergies, dietary issues, cancer.

Why are hypothyroidism and ligament tears more common in neutered and spayed dogs? What conditions have you seen most commonly connected to elevated LH and the inflammatory response?

Dr. Kutzler: The problems we've studied in the lab include hypothyroidism, which occurs several-fold higher in spayed and neutered dogs than in intact dogs.

We've demonstrated that LH receptors are on thyrocytes, the thyroid hormone-producing cells, and that these receptors are located close to receptors for thyroid-stimulating hormone (TSH). When LH binds to its receptor, it disables TSH from triggering thyroid hormone production.

We started with the thyroid gland because of compelling information from human studies showing high LH levels result in hypothyroidism.

Cruciate Ligament Tears in Neutered and Spayed Dogs

Dr. Kutzler: We then focused on musculoskeletal conditions, particularly cruciate ligament rupture. Studies have shown that independent of breed and body condition, the most important factor increasing the tendency toward cruciate ligament rupture is whether the dog has been spayed or neutered.

If a dog ruptures its cruciate ligament on one side, 50% will rupture the other side within a year. While hypothyroidism and cruciate ligament rupture are not typically life-threatening, they significantly affect quality of life.

Dr. Dobias: Absolutely, mobility is crucial for longevity in dogs and humans. Understanding this connection is super important.

Dr. Kutzler: Yes, even basic activities like squatting to go potty can be painful for dogs with untreated cruciate ligament ruptures, leading to inappropriate elimination habits.

Dr. Dobias: Looking at all the tissues and inflammation, are there any conditions not possibly affected by elevated LH? Is it possible that correcting this issue could reduce the frequency of many medical conditions?

Dr. Kutzler: I know a veterinarian in Canada who uses deslorelin implants, a medication that stops the production of the luteinizing hormone. She's seen improvements in dogs with epilepsy and skin allergies.

Dr. Dobias: After neutering my dog Pax, he started getting injured frequently despite physical therapy, acupuncture, and a well-balanced diet. This lasted over two years. However, since our last conversation, Pax has received a deslorelin implant.

Within 24 hours, I could see decreased inflammation, and he was calmer and less anxious. However, I could see the most profound change when I combined deslorelin (Suprelorin) with a weekly injection of testosterone.

Dr. Kutzler: That's wonderful to hear. It's frustrating that deslorelin isn't readily available in the U.S. We need to work on changing the regulatory situation.

Dr. Dobias: Would you measure LH levels first for dogs already spayed or neutered, or go directly to medication? Should they be put on hormone replacement therapy?

Dr. Kutzler: Testosterone supplementation makes sense for male dogs, but it often doesn't work for female dogs. We've used both injectable and oral testosterone. The challenge is that in the USA, testosterone is a controlled substance, and veterinarians may be reluctant to prescribe it due to potential human abuse.

There are also testosterone-related conditions like prostatic enlargement and perianal adenomas to consider.

Dr. Dobias: Is there a difference between oral and injectable testosterone in terms of effect?

Dr. Kutzler: The injectable format is more bioavailable and has a more profound response.

Dr. Dobias: Dr. Linda Brent mentioned her dog Toby is on deslorelin and testosterone supplementation. What minimal dose would you recommend to get the desired effect?

Dr. Kutzler: We had Toby on testosterone for at least three months but couldn't bring LH levels down to single digits. At one point, Toby's LH level was in the 90s, while a normal level is around three or four. This high LH level causes many issues.

Dr. Dobias: Should we measure LH levels in dogs or go directly to deslorelin?

Dr. Kutzler: We've found that LH levels are high in incontinent and continent-spayed dogs. The biological differences between individual dogs likely explain why some develop conditions like urinary incontinence and others don't.

Dr. Dobias: For U.S. dog owners, is there any solution other than changing regulatory situations to access deslorelin and testosterone?

Dr. Kutzler: Virbac manufactures the deslorelin implants, but each country operates independently. Importing the implants from Canada is more accessible now, but veterinarians must review the paperwork for approval.

The ultimate solution is to promote hormone-sparing sterilization and prevent overpopulation responsibly.

Neutered and Spayed Dogs May Suffer from Brain Changes Leading to Aggression

Dr. Dobias: What behavior changes should people look for before trying deslorelin?

Dr. Kutzler: Fear and aggression are two main behavior classifications that become more problematic after spaying and neutering. We've seen a reduction in fear and anxiety behaviors following deslorelin treatment, including separation anxiety.

Dr. Dobias: My service dog Pax became very anxious during flights after being neutered. Since starting the treatment, his anxiety has reduced by 80-90%. This makes sense, given the LH receptors in the amygdala and hippocampus.

Dr. Kutzler: Yes, hormones affect moods and behaviors in humans and animals.

Dr. Dobias: This has been an enlightening conversation. It has transformed my view of many things. Thank you so much for your time. I look forward to our next discussion and working together to provide more information and solutions for dogs worldwide.

Dr. Kutzler: Thank you. I look forward to it, too.

Citations:

• Kutzler, M. A. (2023). Understanding the effects of sustained supraphysiologic concentrations of luteinizing hormone in gonadectomized dogs: What we know and what we still need to learn. Theriogenology, 196, 270–274. https://doi.org/10.1016/j.ther...

• Zwida, K. H., & Kutzler, M. A. (2022). Canine splenic hemangiosarcoma cells express and activate luteinizing hormone receptors in vitro. American Journal of Veterinary Research, 83(12). https://doi.org/10.2460/ajvr.2...

• Zwida, K. H., & Kutzler, M. A. (2022). Canine splenic hemangiosarcoma cells express and activate luteinizing hormone receptors in vitro. American Journal of Veterinary Research, 83(12). https://doi.org/10.2460/ajvr.2...

• Kutzler, M. A., Moccia, V., Zwida, K., & Verena Löhr, C. (2022). Luteinizing Hormone Receptor Expression in Neoplastic Mast Cells Is Increased in Spayed and Neutered Dogs. Journal of the American Animal Hospital Association, 58(6), 271–276. https://doi.org/10.5326/jaaha-...

• Fontes, G. S., McCarthy, R. J., Kutzler, M. A., & Zitek-Morrison, E. (2022). The effects of sex and neuter status on trauma survival in dogs: A Veterinary Committee on Trauma registry study. Journal of Veterinary Emergency and Critical Care (San Antonio, Tex. : 2001), 32(6), 756–763. https://doi.org/10.1111/vec.13...

• Brent, L., Lissner, E. A., & Kutzler, M. A. (2021). Restoration of Reproductive Hormone Concentrations in a Male Neutered Dog Improves Health: A Case Study. Topics in Companion Animal Medicine, 45, 100565. https://doi.org/10.1016/j.tcam...

• Zwida, K., & Kutzler, M. A. (2021). Expression of luteinizing hormone receptor (LHR) in canine lymphoma is not affected by body weight, sex, lymphoma phenotype, and lymphoma stage. Clinical Theriogenology. Published. https://clinicaltheriogenology....

About Dr. Michelle Kutzler

Professional Affiliations: 

1989 - Present - Society for Theriogenology

1989 - Present - American Veterinary Medical Association

1999 - Present - American College of Theriogenologists (Certifying Exam committee, 2013-current)

2000 - Present - Society for Gynecologic Investigation (Scientific Abstract Reviewer, 2003-2014)

2000 - 2012 - European Veterinary Society for Small Animal Reproduction

2002 - 2015 - International Society for the Study of Hypertension in Pregnancy

Education: 

M.B.A - Organizational Leadership, Oregon State University, 2019

Ph.D -  Physiology, Cornell University, 2002

D.V.M. - Washington State University, 1993

B.S. - Veterinary Science, Washington State University, 1990 

Awards and Honors

• Recognition for mentoring multiple honors students, Oregon State University. (September 18, 2023).

• Award of Recognition of Service, Society for Theriogenology. (2022).

• American Kennel Club Sportsmanship Award, Chintimini Kennel Club. (2019).

• Award of Recognition of Service, Society for Theriogenology. (2019).

• Diversity Commitment Award, Oregon State University College of Agricultural Sciences. (2016).

• Sunny Brook Dairy Outstanding Leader Award, Benton County 4-H. (2015).

• Top Prof Award, Oregon State University's Mortar Board Honor Society. (May 2013).

• One of the “25 Most Downloaded Articles” in 2010 (“Non-surgical methods of contraception and sterilization” in Theriogenology), Elsevier. (2011).

• One of the “25 Most Downloaded Articles” in 2009 (“Estrus induction and synchronization in canids and felids” in Theriogenology), Elsevier. (2010).

• Veterinary Honor Roll, Morris Animal Foundation. (October 21, 2004).

• 1st prize in the research abstract competition, European Veterinary Society for Small Animal Reproduction. (May 12, 2002).

• Young Investigator’s Travel Grant, International Society for the Study of Hypertension in Pregnancy. (March 10, 2002).