If you follow dog health accounts online, you have probably seen posts saying that "hormone-sparing" sterilization is healthier than a traditional spay or neuter. Some of them quote a study of more than 6,000 dogs. Others compare an ovary-sparing spay with tubal ligation and warn about infections.
A few of our followers have asked us about it lately, so here is a plain-English look at what these procedures are, what the research found, and the trade-offs that social media posts often leave out.
One thing up front: this is not an argument against spaying. For many families, a traditional spay is still a safe, sensible choice. The goal here is to help you have a better-informed conversation with your vet.
What "Hormone-Sparing" Actually Means
A traditional spay removes a female dog's ovaries, and usually her uterus too. A traditional neuter removes a male dog's testicles. Either way, the principal organs that make the main sex hormones (estrogen, progesterone and testosterone) are gone.
Hormone-sparing procedures still prevent puppies, but they leave the hormone-producing organs in place:
• Ovary-sparing spay (OSS): the uterus and cervix are removed, but the ovaries stay. She can't get pregnant, but her body keeps making its own hormones.
• Tubal ligation: the tubes are tied or cut, but the uterus stays in place.
• Vasectomy (for males): the tubes that carry sperm are cut, and the testicles stay.
Why People Are Talking About It
The study you have probably seen quoted was published in the Journal of the American Veterinary Medical Association (JAVMA) in 2023 (link included in the References below). Researchers reviewed surveys from the owners of 6,018 dogs: intact dogs, traditionally spayed and neutered dogs (in which the gonads were removed), and a smaller group of dogs that had had an ovary-sparing spay or a vasectomy (in which the gonads remained).
The main finding was that the longer a dog had its gonads (and was exposed to its own sex hormones), the lower the odds of general health problems and problem behaviors. That held no matter how the dog was eventually sterilized.
This fits a growing body of research linking early spay and neuter to higher rates of some conditions, including obesity, urinary incontinence, cruciate ligament tears, hypothyroidism and some cancers.
It is worth knowing the limits, though:
• It was an owner survey, not a controlled trial. Owners reported the health problems themselves.
• Many of the owners surveyed were recruited through an association that promotes breeding, meaning that pure-bred dogs were likely over-represented
• The reason for gonadectomies was not reported. Thus, reported conditions may have caused the gonadectomy and not vice versa.
• The hormone-sparing groups were small: 159 ovary-sparing spays and 58 vasectomies, out of more than 6,000 dogs.
• There was a generally low prevalence of reported health conditions, limiting the study’s ability to detect differences across groups
• It shows an association, not proof of cause. It is a strong reason to keep researching, but not a final answer.
Ovary-Sparing Spay vs. Tubal Ligation: The Pyometra Question
This is a point the social media posts get right, and it is an important one.
Pyometra is a serious infection of the uterus, and it can be life-threatening. It is common in intact females: a large Swedish insurance study found that roughly 1 in 4 unspayed female dogs had developed pyometra by age 10. The risk varied a lot by breed, from about 10% to over 50%.
• Tubal ligation leaves the uterus in place, so the pyometra risk stays essentially the same as in an intact female.
• An ovary-sparing spay removes the whole uterus and cervix, so pyometra shouldn't be able to develop, provided every bit of that tissue is removed. If some is left behind, a "stump pyometra" can still happen. That's why the surgeon's experience with this particular procedure matters a lot.
The Trade-Offs of an Ovary-Sparing Spay
These are the parts that rarely make it into a social media graphic:
• She will still have heat cycles. There's no bleeding, because the uterus is gone. But she'll still attract male dogs and may show heat behaviors, so she needs close supervision during those weeks.
• Mammary (breast) tumor risk stays closer to that of an intact female. Removing the ovaries early is one of the main ways a traditional spay reduces this risk. Keeping them means you give up that benefit, and you'll want regular checks for lumps.
• The ovaries are still there, so problems with the ovaries themselves remain possible, although they're uncommon.
• Fewer vets offer it, and it's often recommended only once a dog is fully grown. You may need to look around for an experienced surgeon.
Neither option is "right" for every dog. Size, breed, age, household (other intact dogs, children, how easily you can supervise her during heat) and your dog's own health history all play a part.
Other Considerations
As the authors of the 2023 JAVMA study point out, gonadectomy can prevent the development of testicular tumors, testosterone-induced conditions such as benign prostatic hyperplasia and perianal adenoma, the development of ovarian tumors, and pyometra (with the concurrent removal of the uterus) and may reduce the risk of mammary cancer. By contrast, gonadectomy can increase the risk of prostatic carcinoma and a number of serious cancers in dogs. This is especially so in larger and certain other breeds of dogs. Moreover, gonadectomy is associated with obesity, diabetes mellitus, orthopedic disorders, immune and auto-immune disorders, vaccine reactions, hypothyroidism, pancreatitis, and cognitive impairment. Thus, if your dog is susceptible to one or more of those conditions (due to family or medical history or breed, for example), then that might tilt the balance either in favor of gonadectomy or against. This is definitely a conversation to have with your doctor.
The Hormone Angle Most Posts Miss
Here is the part that connects to what we talk about most on this blog.
The hormones the ovaries and testicles release signal back to the brain, telling it when to stop asking for more. Once they're removed, that feedback stops, and the brain keeps releasing luteinizing hormone (LH) at high levels for the rest of the dog's life. Researchers have measured LH in spayed and neutered dogs at up to 30 times the normal adult level.
LH receptors have been found in tissues well beyond the reproductive organs, including the thyroid, the cruciate ligament and, in some studies, the adrenal glands. Dr. Michelle Kutzler at Oregon State University and others are investigating whether constantly high LH explains some of the long-term health effects seen after spay and neuter.
There is also early evidence connecting this to the adrenal glands specifically. In one small study of spayed female dogs with Cushing's syndrome, 8 of 14 showed an increase in cortisol when their adrenal glands were stimulated with an LH-like hormone. That response was more likely in dogs spayed later in life. This tracks with research in humans, which shows an increase in androgens and/or cortisol upon activation of LH receptors in the adrenal glands.
This research is still young, and it doesn't mean that spaying causes Cushing's. But it does help explain why hormone balance, and not just cortisol, keeps coming up when vets talk about adrenal problems in dogs.
Where Lignans Fit In
If your dog is already spayed or neutered, there is no need to worry. Most spayed and neutered dogs live long, healthy lives.
What's worth doing for any dog, but especially one that has undergone a gonadectomy, is watching for signs of a hormone or adrenal imbalance, especially as your dog gets older: a thinning coat or hair loss, a pot-bellied look, drinking and urinating much more than usual, or skin changes. If you notice them, talk to your vet about testing.
If LH is causing your dog to show any signs of Cushing’s Syndrome (such as the ones listed in the preceding paragraph), you should discuss it with your veterinarian. For these dogs, veterinarians at the University of Tennessee have used a combination of flaxseed lignans and melatonin. Lignans are plant compounds that, in combination with melatonin, inhibit the manufacture of cortisol and other Cushing’s related adrenal hormones. We cover this in more depth in our guide to atypical Cushing's disease in dogs and our post on melatonin for dogs with Cushing's.
If you and your vet decide lignans are worth trying, you can browse our flaxseed lignans for dogs. Please check the dose for your dog's weight with your vet, especially if your dog is on other medications.
For a more technical look at the adrenal research, our sister site has a summary of the study on adrenal disorders in dogs.
Questions to Ask Your Vet
If you are weighing up options for a new puppy or a young dog, these are good questions to bring to your appointment:
1. Do you perform ovary-sparing spays or vasectomies, and how many have you done?
2. For my dog's breed and size, what age would you recommend for sterilization, and why?
3. How would we manage heat cycles safely after an ovary-sparing spay?
4. What does mammary tumor screening look like if she keeps her ovaries?
5. If my dog is already spayed or neutered, which signs of a hormone or adrenal imbalance should I watch for as they get older?
6. Does my dog’s medical history indicate any susceptibility to any of the conditions listed under “Other Conditions”, above?
The Bottom Line
The research on hormone-sparing sterilization is interesting and growing, and the pyometra point about tubal ligation versus ovary-sparing spay is real. But the evidence is still early. The main study is an owner survey with small hormone-sparing groups, and an ovary-sparing spay has genuine trade-offs of its own.
The best choice depends on your individual dog. Bring these questions to your vet, and make the decision together.
Sources
• Zink C, Delgado MM, Stella JL. Vasectomy and ovary-sparing spay in dogs: comparison of health and behavior outcomes with gonadectomized and sexually intact dogs. JAVMA, 2023; 261(3):366–374.
• Egenvall A, Hagman R, Bonnett B, Hedhammar A, Olson P, Lagerstedt A. Breed risk of pyometra in insured dogs in Sweden. Journal of Veterinary Internal Medicine, November 2001, Volume 15, Issue 6:530–538
• Kutzler MA. Possible relationship between long-term adverse health effects of gonad-removing surgical sterilization and luteinizing hormone in dogs. Animals (Basel). 2020 Apr 1;10(4):599..
• Espiñeira IM, Vidal PN, Ghersevich MC, Soler Arias EA, Bosetti F, Cabrera Blatter MF, Miceli DD, Castillo VA. Adrenal cortex stimulation with hCG in spayed female dogs with Cushing's syndrome: is the LH-dependent variant possible? Open Vet J. 2021 Apr-Jun;11(2):319-329
• Rao CV. Human adrenal LH/hCG receptors and what they could mean for adrenal physiology and pathology. Molecular and Cellular Endocrinology, 2010; 329, Issues 1–2:33-36
This article is for general information and is not a substitute for veterinary advice. Always talk to your veterinarian before making decisions about surgery, supplements or your dog's health.