My dog Pax was two years old when I had him neutered. He was a young, athletic dog — strong, eager, full of life — and I made the decision for all the reasons veterinarians have given pet owners for decades: it was the responsible thing to do. Dogs are better off, healthier, and less frustrated when neutered.
What I did not expect was what came next.
Pax’s Story
Within months of his surgery, Pax started getting injured. First it was occasional lameness, which grew into one injury after another. A young dog who should have been in peak condition became chronically lame.
He also began overheating at night, leaving his bed for the cool bathroom floor. He panted more than before. His muscles softened and shrank. His coat dulled and grew shorter. The joy and spark that had defined him — that eagerness to work, to play, to engage — faded unexpectedly.
I did what any vet would do. I treated what I could see. I tried rehabilitation. Anti-inflammatory treatments. Acupuncture. Frankly, I tried everything in my toolkit. Nothing worked in any lasting way. Pax would improve briefly, then break down again. I was about to schedule platelet-rich plasma therapy when the specialist’s waitlist gave me something I thought I hadn’t had: time.
Time to stop treating and start searching.
It didn’t occur to me — not at first, and not for longer than I’m comfortable admitting — that the absence of testosterone and the constant rise of a hormone called luteinizing hormone (LH) could be at the root of everything I was seeing. I was trained to think of neutering as a solved question. A net positive. A routine procedure with no real systemic consequences. It simply wasn’t on my radar.
But the more I searched, the more the evidence pointed to one conclusion I couldn’t ignore: spaying and neutering — the very procedures I had performed thousands of times and recommended without hesitation — could be causing my own dog’s decline.
My search led me to the work of two researchers who would completely change how I practice veterinary medicine: Dr. Linda Brent of the Parsemus Foundation and Dr. Michelle Kutzler at Oregon State University. Without their published research, their willingness to challenge established thinking, and their generosity in sharing their clinical frameworks, Pax’s story would have ended very differently. And this article would not exist. However, I was fortunate to have the research and guidance early on in 2024. Only four months after I started the hormone replacement protocol I describe in this article.
Pax fully recovered and has been injury free ever since. He celebrated his 7th birthday in 2026.
My experience didn’t just challenge conventional wisdom. It indicted it. And there was nothing more important than to share the information with others. Since then, I have witnessed similar responses in several other dogs. Reliable, positive, side-effect free results.
I trust you will find the following information helpful and inspiring. If your dog is neutered or spayed, you can see them thrive and live healthier lives. If you have a puppy that has not been altered yet, hormone sparing methods — such as vasectomy and ovary sparing spays — are a safer, better choice for controlling unwanted pregnancies. WSAVA also recommends that dogs living with responsible guardians can also be left intact. To say this, female dogs are at 25% risk of pyometra, and hormone sparing spay may be the best choice.
How a Medical Procedure Became “Just What You Do”
To understand why we’re here, we need to go back to where this started. The routine surgical removal of a dog’s reproductive organs is not an ancient medical tradition backed by centuries of evidence. It started out of surgical convenience. Dr. Karen Becker, DVM, one of North America’s leading integrative vets, traced this practice back to Iowa State College of Veterinary Medicine — often cited as the first veterinary college in the world, founded in 1895. When she asked the dean about the historical reasoning, the answer was disarmingly honest: “When the surgical site was open, we would just take everything — because why not?” That “why not” became the unquestioned foundation of small animal veterinary medicine. As anesthesia became available in the early 1900s and dog overpopulation became a real problem, spay/neuter was promoted as the humane solution. The profession built a supporting story around it:
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- Neutering reduces aggression and roaming
- Removing the reproductive organs is simply better for domestic dogs
These ideas were taught as facts in veterinary schools across North America and passed from generation to generation — from vets to dog guardians. Today, 64% of dogs in the United States are surgically sterilized, most often between six weeks and twelve months of age. In 30 U.S. states, it is legally required for any dog adopted from a shelter. It has become so normal that many owners don’t even think of it as a medical decision. It’s just what you do.
What the profession failed to ask — for nearly a century — was this: What happens to the rest of the body when you permanently remove the organs that make its key hormones?
We are now getting the answer. And it is shocking.
The Leaky Toilet: Your Dog’s Hormone System Explained
Your dog’s body runs a beautifully balanced hormone loop. Here’s how it works:
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- A small but powerful part of the brain called the hypothalamus that connects the sensory inputs into hormonal responses.
- It sends signals to the pituitary gland — the body’s master hormone controller.
- The pituitary releases LH (luteinizing hormone), which travels through the bloodstream to the reproductive organs.
- The reproductive organs respond by making testosterone, estrogen, and progesterone.
- Those hormones then circle back and signal the pituitary: “Enough!” LH slows down. Balance is maintained.
I call this the “leaky toilet” principle. In a properly working toilet, the rising water lifts the float and cuts off the flow. In a healthy hormone system, rising sex hormones cut off LH.
But remove the reproductive organs, and the tank is permanently empty. The float never rises. LH keeps flooding the body — not in the normal bursts of a healthy cycle, but constantly, relentlessly, at levels far beyond anything the body was designed to handle.
Dr. Michelle Kutzler, DVM, PhD, is a board-certified veterinary reproductive specialist and professor at Oregon State University. She has spent more than a decade studying exactly what this means. Her research, published across multiple peer-reviewed journals, paints a picture that should alarm anyone who has assumed that removing the reproductive organs is a harmless procedure.
In dogs that have been spayed or neutered, LH levels can be more than 30 times higher than in intact dogs — reaching up to 100 ng/mL compared to less than 1 ng/mL in dogs who still have their reproductive organs. These are not slightly elevated levels. They are an astronomical, non-stop flood of a hormone going to places it was never meant to go.
Here is the most critical discovery: LH receptors exist in almost every tissue in your dog’s body. They have been found in the thyroid gland, adrenal glands, gut, joints, joint cartilage, bone, immune cells, blood vessels, the brain, the bladder, and the skin. When those tissues are constantly bombarded by abnormally high LH levels, the result is not a reproductive problem. It is a whole-body inflammatory response that touches every organ system at once.
This is not a theory. It is a mechanism documented in published, peer-reviewed research. Through desexing, we have unintentionally created preventable diseases in our most beloved animals.
What the Research Shows: Real Diseases, Real Dogs
The list of health conditions occurring at higher rates in spayed and neutered dogs has grown steadily as researchers have followed the evidence. This is not advocacy or opinion. These are published findings from peer-reviewed studies in major veterinary journals.
Cancer
The cancer data is where the picture gets starkest. The reproductive organs are not merely for reproduction — as Dr. Kutzler writes in her landmark 2022 paper: they are “necessary endocrine glands for normal metabolic, endocrinologic, musculoskeletal, and anti-neoplastic health.” Remove them, and the body’s natural cancer defenses are weakened at multiple levels at once.
Hemangiosarcoma is an aggressive blood vessel tumor that kills most dogs within months of diagnosis. It occurs at 2 to 10 times the rate in spayed females compared to intact females. The cardiac form specifically is five times more common. A large study of over 2 million dogs confirmed significantly elevated risk in both spayed females and neutered males. Even more striking: when hemangiosarcoma cells are exposed to LH in the lab, they multiply. The hormone doesn’t just correlate with the tumor — it appears to feed it.
Lymphoma is 3 to 4 times more common after spay/neuter in the general dog population. In male Golden Retrievers neutered before 12 months, the lymphoma rate is triple that of intact males — roughly 1 in 10 develops the disease. Research shows that up to 45% of cancerous T-lymphocytes (a type of immune cell) carry LH receptors, and that LH activation increases their growth, spread, and invasiveness. Again: the mechanism is documented.
Prostate cancer presents a surprise that overturns what most vets were taught. Neutering was long believed to protect against prostate cancer in dogs. In fact, the opposite is true. Neutered male dogs have approximately four times the rate of prostate cancer compared to intact males. This is one of the most thoroughly documented reversals in small animal cancer research.
This finding also raises a broader question worth sitting with: could the natural decline of testosterone in aging men be somehow connected to prostate cancer risk in humans as well?
Osteosarcoma (bone cancer) risk increases in dogs neutered before one year of age, particularly in large and giant breeds. In Rottweilers — already a predisposed breed — males and females neutered before their first birthday had 3.8 and 3.1 times the bone cancer risk, respectively, compared to intact dogs.
Orthopedic Disease
The joint and bone consequences of early spay/neuter begin in the growth plates. Sex hormones — especially estrogen — are needed for growth plates to close at the right time. Remove those hormones before puberty, and the plates stay open longer. Bones keep growing past their ideal length and shape. This leads to abnormal joint angles and mechanical problems that cause degenerative disease throughout the dog’s life.
Torn knee ligament (CCL) — the dog version of an ACL tear, and one of the most common and expensive surgeries in veterinary medicine — is twice as common in spayed and neutered dogs as in intact animals. A major 2024 systematic review confirmed this connection, especially in dogs spayed or neutered at or before one year of age. In one study of intact Golden Retrievers, zero dogs had CCL disease. Among early-neutered males, the rate was 5%. Among early-neutered females, it was 8%.
Hip dysplasia risk increases 1.5 to 2 times, with the strongest effect in neutered males. In Labrador and Golden Retrievers neutered before six months, joint disorder rates doubled and quadrupled, respectively, compared to intact dogs.
Metabolism and Hormones
Spay/neuter is the single largest risk factor for obesity in dogs. Up to 68% of spayed and neutered dogs become obese. Food intake increases by 20% within just one week of surgery — and that increased hunger never goes away. This happens not because your dog is greedy. It happens because the hormones that regulate hunger, fullness, and energy use have been surgically removed.
Spay/neuter also doubles the risk of diabetes. Spayed and neutered dogs develop hypothyroidism (an under-active thyroid) 30% more often than intact dogs.
The thyroid connection deserves special attention. LH receptors sit right alongside thyroid-stimulating hormone (TSH) receptors in your dog’s thyroid cells. When LH floods those cells constantly, it interferes with how thyroid hormones are made. The result is a condition sometimes called euthyroid sick syndrome — where thyroid lab tests look technically normal, but the dog is genuinely not producing enough active thyroid hormone and is metabolically compromised. This is almost certainly a major driver of the epidemic of “idiopathic hypothyroidism” we see diagnosed in neutered dogs. We are treating the symptom, not the cause.
Behavior and Brain Health
The behavioral effects of spay/neuter are poorly understood by most practitioners — partly because they’re hard to connect to a surgery performed months or years earlier, and partly because the profession taught for decades that neutering reduces problem behavior. The evidence now points in the opposite direction.
Testosterone and estrogen are essential building blocks for dopamine — the brain chemical tied to happiness, motivation, and joy. Remove those hormones, and dopamine production drops significantly. The natural question is: how does that affect a dog’s well-being and quality of life?
The answer, increasingly backed by research, is: profoundly. Published studies show that neutered dogs are more aggressive and more fearful than intact dogs — the precise opposite of what we were taught. LH receptors in the amygdala and other emotional centers of the brain, when chronically flooded with abnormally high LH, drive neuroinflammation (inflammation in the brain). Cognitive dysfunction syndrome — the dog equivalent of Alzheimer’s disease — occurs at higher rates in spayed and neutered dogs.
The Veterinary Profession Is Starting to Shift
In May 2024, the World Small Animal Veterinary Association (WSAVA) published its first-ever Global Guidelines for the Control of Reproduction in Dogs and Cats in the Journal of Small Animal Practice.
These guidelines, developed by an international committee of veterinary reproductive specialists, moved away from the traditional approach of routine spay/neuter for all owned animals. They officially endorsed two alternatives:
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- Ovary-sparing spay (removing only the uterus, keeping the ovaries)
- Vasectomy (for male dogs)
They also recommended against spay/neuter before puberty and acknowledged that, for responsible pet owners, keeping a dog hormonally intact is a valid choice.
For those of us who have been advocating for this science, the WSAVA shift is validation. For the profession as a whole, it is an institutional admission that the balance of harm and benefit has changed — and that the old assumptions can no longer hold.
And yet only 2 of 38 veterinary schools in the United States and Canada offer any instruction in alternative sterilization techniques. The gap between what the evidence now supports and what veterinary schools teach is enormous. Dr. Kutzler’s own survey at AVMA annual meetings in 2017 and 2018 found that while 73% of veterinarians discussed the long-term health risks of spay/neuter with clients, only 7% actually offered any alternative procedure.
The knowledge is there. The behavior hasn’t caught up.
The Solution: Hormone Replacement Therapy (HRT)
For the millions of dogs already spayed or neutered — including my own dog Pax — the question is not theoretical. The reproductive organs are gone. What can we do now?
The answer emerging from clinical practice and early research is hormone replacement therapy (HRT): restoring sex hormones to healthy levels and, critically, reducing the chronic LH elevation that drives so much damage downstream.
A Story of Recovery: Toby
The first published case report of hormone restoration in a neutered dog appeared in 2021, co-authored by Dr. Linda Brent, PhD (Executive Director of the Parsemus Foundation), Elaine Lissner, and Dr. Michelle Kutzler. The subject was Toby — Dr. Brent’s own dog, adopted from a county shelter at seven months old and mandatorily neutered. Within months, Toby developed rapid weight gain, lost mobility due to severe right hip pain, and became debilitatingly fearful of strangers. Three years of standard veterinary treatment — pain medication, joint supplements, thyroid medication, antidepressants — produced minimal improvement. He was essentially housebound from anxiety.
When Dr. Brent and Dr. Kutzler began hormone restoration, Toby’s life turned around. His protocol combined weekly testosterone cypionate injections under the skin at 0.5 mg/kg with a deslorelin acetate (Suprelorin) implant to suppress the chronic LH elevation. Within months, his mobility returned. His weight stabilized. His fear and anxiety became manageable. He could run, jump, and visit public parks again. As of 2024, Toby has been on the protocol for over five years — and continues to thrive.
The Protocol for Male Dogs
The protocol I use for Pax follows the same framework, informed by Dr. Kutzler’s published research and clinical experience:
Component 1 — Testosterone Replacement
Testosterone cypionate is given by weekly injection under the skin at 0.5 mg/kg. Weekly dosing is essential. Monthly injections at higher doses create hormonal roller-coaster patterns that are destabilizing rather than therapeutic. The first formal safety study of this protocol, published in BMC Veterinary Research in July 2025, confirmed that weekly injectable testosterone is safe in neutered dogs across all tested doses over 90 days, with testosterone levels restored to the normal range for intact dogs.
Component 2 — LH Suppression
A Suprelorin (deslorelin acetate) implant is placed under the skin every six months. This implant works by first causing a brief LH surge, then desensitizing the pituitary gland and suppressing LH production going forward. Testosterone supplementation alone does not normalize LH — the implant is necessary to address the underlying inflammatory component.
The results I have seen in Pax, now seven years old — and that Dr. Karen Becker has documented in her rescue dog Homer, now eighteen years old — are undeniable.
Muscle mass recovered. Coat quality returned. Injuries stopped. Energy and engagement came back. Most significantly: the spark and personality returned.
Pax’s transformation brought his joy of life back. He is happy, alert, eager to work and play and engage. He has been injury free.
The results are not a subjective impression. It is the observable result of a brain receiving adequate dopamine, a musculoskeletal system receiving the anabolic support it needs, and an immune system no longer being chronically disrupted by LH flooding.
Protocols for Female Dogs
The female protocol is less standardized than the male — and that is worth acknowledging honestly. The research base for female dog HRT is thinner, and the ideal combination of estrogen, testosterone, and LH suppression is still being investigated. Dr. Kutzler’s published protocol uses estriol or diethylstilbestrol (a type of estrogen) 0.5 – 1 mg per dog/ day , combined weekly testosterone 0.25mg/kg, and Suprelorin implant every six months.
Both estrogen and testosterone matter in females — females actually produce more testosterone by quantity than estrogen, and testosterone plays essential roles in muscle strength and mental well-being. Some vets are now using low-dose testosterone in spayed females with musculoskeletal issues and repeated injuries, with meaningful results.
For female dogs, the protocol ideally includes a baseline LH measurement before treatment begins. This helps document how elevated LH is and allows tracking of the response. However, Colorado State University’s Veterinary Endocrinology Laboratory that used to offer this test no longer offers it. That said, any dog spayed or neutered for more than six months can reasonably be assumed to have markedly elevated LH — which is why testing before initiating therapy, while helpful, may be considered optional.
Prevention: The Better Path Forward
The best approach, of course, is not hormone restoration after the fact — it’s prevention. The goal is to keep sex hormones intact while eliminating the risk of unwanted reproduction. Two surgical approaches accomplish this.
Ovary-Sparing Spay (Hysterectomy)
The uterus is removed while both ovaries are preserved. This eliminates the risks of pregnancy and pyometra (a life-threatening uterine infection) while maintaining full ovarian hormone production. The ovaries — not the uterus — are responsible for more than 98% of a female dog’s sex hormone production. A female who has had this procedure continues to show signs of normal heat cycles (behavioral changes and vulval changes) but cannot become pregnant and will not have bloody discharge. Dr. Kutzler has been performing and teaching this procedure since 2011, when she produced the first instructional video in partnership with the Parsemus Foundation. The WSAVA 2024 guidelines explicitly recommend it as a legitimate alternative, especially for breeds prone to gonadectomy-associated health problems.
Some veterinarians and shelters have raised concerns about the time this procedure requires. However, Dr. Maricel Lichuan has performed thousands of these surgeries using a flank approach in the Philippines and reports that they do not require additional time compared to a conventional spay.
Vasectomy
The tubes that carry sperm (the vas deferens) are cut, preventing sperm transport while leaving the testicles fully intact. The dog retains complete testosterone production and all secondary sex characteristics. Sperm is absent from the ejaculate within 24 hours of the procedure. Dr. Lichuan has also performed vasectomies at scale and reports that the procedure can be completed in the same time — or less — as a traditional neuter once the technique is mastered. The AVMA recognizes both vasectomy and hysterectomy as acceptable sterilization methods.
The barriers to wider adoption of these techniques are structural, not scientific. They are not taught in veterinary school. They require learning a new surgical approach without a mentor. And the shelter system — constrained by state mandates, high surgical volume, and institutional resistance to change — has been almost entirely unmoved.
This is something we all need to work on changing.
The Researchers Driving This Change
Behind every major scientific advance is someone willing to ask the question the field has decided not to ask. In canine hormone health, three figures have done the foundational work.
Dr. Michelle Kutzler is the scientist who opened up the mechanism. Her 2020 paper in Animals — “Possible Relationship between Long-Term Adverse Health Effects of Gonad-Removing Surgical Sterilization and Luteinizing Hormone in Dogs” — synthesized the LH hypothesis for the first time and documented the spread of LH receptors throughout virtually every tissue in the body. Her 2022 Theriogenology paper extended this to cancer biology, showing that LH receptor activation drives growth of hemangiosarcoma and lymphoma cells. Her laboratory continues to investigate whether GnRH agonist implants might extend remission times in dogs with LH receptor-positive tumors — a potential breakthrough of enormous importance.
Her published conclusion deserves to be read in every veterinary school in the world: “Gonads should no longer be considered mere gamete-producing or ancillary sex organs but rather necessary endocrine glands for normal metabolic, endocrinologic, musculoskeletal, and anti-neoplastic health.”
Dr. Linda Brent of the Parsemus Foundation has been the organizational force connecting research to real-world clinical practice. Under her leadership, Parsemus published the first case report of hormone restoration in a neutered dog, funded and co-authored the first safety and dosing study for injectable testosterone in neutered males, and built and maintains the veterinary directory of practitioners offering hormone-sparing sterilization and HRT. She has built a growing body of peer-reviewed and public-facing literature to establish both the clinical and ethical framework for this work. “The bottom line,” she has said, “is that the longer dogs have their natural hormones, the healthier they are.”
HormoneHealthForDogs.org is an initiative I launched with my colleague Dr. Karen Becker in 2025. Our goal is to bring this groundbreaking science to a broader public audience. This community platform is designed to connect owners and veterinarians around this emerging field, fund research, and create change from the ground up.
Where We Go From Here
I am under no illusion that this field is mature. The 2025 safety study in BMC Veterinary Research — the first formal target-animal safety trial for testosterone replacement in neutered dogs — involved twelve dogs over ninety days. The case literature is made up primarily of individual dogs whose outcomes Dr. Becker and I have documented alongside Dr. Brent and Dr. Kutzler. Controlled, randomized clinical trials are urgently needed. Dr. Kutzler herself has called for them explicitly.
What we do have is mechanism, coherence, and a growing clinical record. The mechanism — chronic LH flooding driving system-wide inflammation across every tissue that carries LH receptors — is documented in multiple peer-reviewed papers with clear molecular evidence. The coherence is striking: a single hormonal disruption explains dozens of diseases that veterinary medicine has been treating in isolation for decades. And the clinical record, while not yet statistically mature, points consistently in one direction.
We have to come to terms with the fact that our profession, despite the best of intentions, contributed to the occurrence of degenerative diseases in dogs. We didn’t know this was the case. But now we do.
Once we know, we cannot ‘un-know’. Once the mechanism is clear, the obligation to inform and to act is the only way forward.
My strong belief, after years of clinical observation and careful engagement with this research, is that a large proportion of the chronic, degenerative conditions seen in veterinary practice today are directly or partially connected to the hormonal depletion caused by conventional spay and neuter procedures in otherwise healthy animals. A growing body of research supports this.
For owners of dogs already spayed or neutered: HRT is an option worth exploring seriously. Find a veterinarian trained in integrative or functional medicine. The Parsemus Foundation and the American Holistic Veterinary Medical Association maintain searchable directories.
For owners planning sterilization: Ask about ovary-sparing spay or vasectomy. Ask whether your veterinarian performs them. If the answer is no, find one who does — or ask your vet to learn.
For veterinarians reading this: The WSAVA has moved. The literature is moving. The question is no longer whether sex hormones matter to whole-dog health — they do, extensively and mechanistically. The question is what we do with that knowledge.
What I have learned from Pax, from Toby, and from the other dogs going through hormone restoration is that dogs come to us equipped with a hormone system that evolved over millions of years. That system is not incidental to their health. It is the foundation.
When we remove it — as a routine act, without conversation, without offering alternatives, without understanding what we are taking away — we are making a decision on behalf of an animal who cannot consent, based on assumptions that the evidence is now overturning. That is a responsibility that demands better.
My dog Pax is swimming and running and hiking again. He is happy, alert, engaged, and joyful. What I am witnessing is possible for millions of dogs around the world.
Frequently Asked Questions (FAQ)
Q: Is it bad to spay or neuter my dog?
Spaying and neutering are very common procedures, but new research shows they can cause long-term health problems — including joint injuries, cancer, obesity, and behavioral changes. This is because removing the reproductive organs causes a hormone called LH to flood the body at dangerously high levels. Hormone-sparing alternatives now exist and are worth discussing with your vet.
Q: What is luteinizing hormone (LH), and why does it matter for dogs?
LH is a hormone made by the brain’s pituitary gland. In intact dogs, the reproductive organs keep LH levels in balance. When those organs are removed, LH floods the body constantly — at 30 to 100 times the normal level. Because LH receptors exist in almost every tissue in the body, this flood causes inflammation, disease, and organ dysfunction throughout the whole body.
Q: What health problems are linked to spaying and neutering?
Research links spay/neuter to a wide range of conditions, including:
- Torn knee ligaments (CCL tears)
- Hip dysplasia
- Bone cancer (osteosarcoma), lymphoma, and hemangiosarcoma
- Prostate cancer (higher risk in neutered males, not lower)
- Obesity and diabetes
- Hypothyroidism (underactive thyroid)
- Increased fear and aggression
- Cognitive decline (dog dementia)
Q: What is an ovary-sparing spay?
An ovary-sparing spay removes only the uterus, leaving both ovaries intact. This prevents pregnancy and serious uterine infections (pyometra) while allowing the ovaries to keep making hormones. The WSAVA endorsed it in 2024 as a safe, legitimate alternative to traditional spaying.
Q: What is a vasectomy for dogs?
A vasectomy cuts the tubes that carry sperm, so the dog can no longer father puppies. The testicles stay intact and keep producing testosterone. All the health benefits of male hormones are preserved. The AVMA recognizes this as an acceptable sterilization method.
Q: What is hormone replacement therapy (HRT) for dogs?
Dog HRT involves restoring sex hormone levels in dogs that have already been spayed or neutered. For males, this typically means weekly testosterone injections plus a Suprelorin implant to suppress LH. For females, it may include estrogen and/or testosterone along with a Suprelorin implant. Clinical results have been very encouraging — including improved mobility, weight, coat, energy, and mood.
Q: What is a Suprelorin (deslorelin) implant?
Suprelorin is a small implant placed under your dog’s skin, usually every 6–12 months. It works by signaling the brain to stop overproducing LH. It is a key part of hormone restoration because testosterone alone doesn’t fully stop the LH flood — you need both components working together.
Q: My dog is already spayed or neutered. Is it too late to help?
It’s not too late. Hormone replacement therapy can be started at any age after sterilization. Dogs like Toby and Pax have shown significant improvement even years after surgery. Talk to a holistic or integrative vet about testing LH levels and exploring a protocol.
Q: Does keeping my dog intact make them harder to manage?
Not necessarily. Responsible management — keeping dogs leashed, secured, or supervised — prevents unwanted breeding. Many intact dogs are calm, well-mannered, and healthy. Hormone-sparing sterilization also gives you the best of both worlds: no risk of unwanted puppies, and no loss of protective hormones.
Q: Where can I find a vet who offers hormone-sparing sterilization or HRT for dogs?
- parsemus.org — veterinary directory for hormone-sparing sterilization providers
- ahvma.org — American Holistic Veterinary Medical Association member directory
- hormonehealthfordogs.org — community platform and resources by Dr. Peter Dobias and Dr. Karen Becker
Q: What did the WSAVA say about spay and neuter in 2024?
In May 2024, the World Small Animal Veterinary Association published its first-ever global reproduction guidelines. They officially endorsed ovary-sparing spay and vasectomy as legitimate alternatives and recommended against early (prepubertal) spay/neuter. They also acknowledged that keeping a dog hormonally intact is a valid choice for responsible owners.
Q: Can a dog with cancer benefit from hormone replacement therapy?
Possibly — and this is an active area of research. Dr. Kutzler’s laboratory is investigating whether Suprelorin implants can extend remission in dogs with LH receptor-positive tumors, such as certain types of lymphoma and hemangiosarcoma. If your dog has already been diagnosed with cancer, this is worth discussing with an oncologist familiar with this research.
Q: Is there a blood test to check LH levels in my dog?
Yes. Colorado State University’s Veterinary Endocrinology Laboratory offers LH testing for dogs. Measuring LH before starting HRT gives you a useful baseline to track the response to treatment. That said, most vets familiar with this protocol agree that any dog spayed or neutered for more than six months will have markedly elevated LH — so testing is helpful but not always required before starting.
Q: Why do neutered dogs eat more and gain weight so quickly after surgery?
It’s not about willpower or overfeeding. Within one week of surgery, food intake increases by about 20% — and this stays elevated permanently. Sex hormones regulate hunger signals and energy use. Without them, the brain’s fullness signals stop working properly. The dog feels hungry even when they’ve eaten enough — because the hormonal system that would normally say “stop” no longer exists.
Q: Can neutering make my dog more aggressive?
Research shows it can, yes. This is the opposite of what most people have been told. Testosterone and estrogen support dopamine production and emotional regulation. Without them, some dogs become more fearful and reactive. LH flooding the amygdala — the brain’s fear and emotion center — may also directly drive anxiety and aggression.
Q: Does a vasectomy change a male dog’s personality or behavior?
Generally, no — and not in a negative way. Since the testicles remain intact, testosterone production continues as normal. Some sexually motivated behaviors (like roaming or marking) may persist in some dogs, but the dog’s core personality, energy, and happiness are preserved. Many guardians report their intact or vasectomized male dogs are more emotionally stable overall than neutered dogs.
Q: What is the difference between a traditional spay and an ovary-sparing spay for long-term health?
In a traditional spay, both the ovaries and uterus are removed — eliminating all sex hormone production and triggering the chronic LH flood. In an ovary-sparing spay, only the uterus is removed. The ovaries keep functioning and producing hormones. This means the dog avoids LH flooding, metabolic disruption, and the increased disease risks associated with full gonadectomy — while still being unable to become pregnant.
Q: Can I give my dog testosterone I find online or over the counter?
No. Dog HRT protocols require specific pharmaceutical-grade medications, precise dosing by body weight, and active veterinary oversight. Using the wrong product, dose, or schedule can cause serious harm. The current protocol uses weekly injectable testosterone cypionate — not topical products, supplements, or human formulations. Always work with a licensed veterinarian trained in this area.
Q: What is euthyroid sick syndrome in dogs?
This is a condition where thyroid test results appear normal on paper, but the dog is not actually producing enough active thyroid hormone to function well. It’s caused by chronic LH flooding of the thyroid cells, which disrupts the conversion of T4 (inactive thyroid hormone) to T3 (the active form the body uses). Many spayed or neutered dogs may be living with this condition — feeling sluggish, gaining weight, and losing coat quality — while their blood tests show up as technically “normal.”
Q: Are shelters moving toward hormone-sparing sterilization?
Very slowly, and not yet meaningfully. Despite advocacy and even offers of financial support, most shelters in the U.S. remain committed to traditional spay/neuter. State mandates, high surgical volume, and deeply ingrained institutional habits are the main obstacles. Author Ted Kerasote contacted shelters across the country offering a $5,000–$10,000 bond and veterinary certification for hormone-sparing procedures — and not a single shelter accepted. Meaningful change will require action at the policy level, not just in private practice.
Research References
1. Kutzler MA. Possible Relationship between Long-Term Adverse Health Effects of Gonad-Removing Surgical Sterilization and Luteinizing Hormone in Dogs. Animals (Basel). 2020;10(4):599. https://doi.org/10.3390/ani10040599
2. Kutzler MA. Understanding the effects of sustained supraphysiologic concentrations of luteinizing hormone in gonadectomized dogs. Theriogenology. 2022;196:270–274. https://doi.org/10.1016/j.theriogenology.2022.11.007
3. Kutzler MA. Gonad-Sparing Surgical Sterilization in Dogs. Frontiers in Veterinary Science. 2020. https://doi.org/10.3389/fvets.2020.00342
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