As research has revealed more health risks linked to canine gonadectomy, veterinarians have become less inclined to treat spaying and neutering surgery as universally appropriate and consequence-free. A recent review published in the Journal of Small Animal Practice strongly supports a more individualized approach to sterilization. This underscores the potential benefits of hormone-sparing procedures.
The groundbreaking WSAVA guidelines
In February 2025, the World Small Animal Veterinary Association (WSAVA) published Guidelines for the Control of Reproduction in Dogs and Cats. This comprehensive document organizes vast amounts of scientific information about dog and cat sterilization methods. It discusses how they’re performed, the outcomes of various methods, and recommendations.
The lead author of the WSAVA Guidelines, Professor Stefano Romagnoli of the University of Padova, Italy, is also the author of the latest review on dog gonadectomy (or spay and neuter). He summarizes the accumulated evidence of the effects of traditional spaying and neutering on the health of companion dogs. The goal is to help veterinarians and dog parents determine whether to spay or neuter dogs and, if so, the best age to do so.
The historical benefits of traditional dog sterilization
Surgical spaying and neutering have been the primary methods for reproductive control in many parts of the world. Gonadectomy involves the removal of the testes in males and the ovaries (and often the uterus) in females. This also removes the sex hormones normally produced by those organs.
Canine spay and neuter procedures have played a crucial role in managing pet overpopulation. They have also reduced certain undesirable behaviors, such as roaming and marking. The review confirms that traditional spaying and neutering are preventive measures for diseases of the reproductive tract or those dependent on sex hormones:
- Females: Prevents risk of mammary tumors and pyometra (a life-threatening uterine infection).
- Males: Lowers the risk of enlargement of the prostate (benign prostatic hyperplasia) and prevents diseases of the testes.
Given the importance of reducing pet overpopulation and the widespread belief that gonadectomy improves the health of companion dogs, the suggested age for gonadectomy was lowered over time to prepubertal and even pediatric ages, based on the assumption that an earlier, technically simpler surgery would benefit the pet.
Research has shown that these assumptions were misguided.
A closer look at gonadectomy outcomes
Research on the health impacts of gonadectomy over almost 20 years has raised concern. A variety of serious health conditions – including cancer and orthopedic disorders – occur more commonly in spayed/neutered dogs than in intact dogs. For several health conditions, the earlier the age of gonadectomy, the higher the risk. Also, instead of expected improvements in behavior, gonadectomy has been related to unwanted behavioral changes.
“This new information is causing a change of paradigm, and the ongoing discussion among small animal practitioners is leading many to wonder what is the best age for gonadectomy and whether dog owners should not be advised to spay/neuter their animals any longer.”
— Prof. Stefano Romagnoli, Journal of Small Animal Practice
Increased health risks associated with hormone loss
The core of the paper addresses the growing evidence that removing the sex hormones through traditional gonadectomy is associated with an increased incidence of numerous disorders. This emerging data challenges the traditional practice of prepubertal or pediatric spay/neuter and encourages reconsideration of gonadectomy for all dogs.
The author emphasized that definitive conclusions on the role of gonadectomy are difficult to reach for all conditions. This is due to multifactorial causes and variations in study methodology. However, the consistent reporting of increased risks for certain cancers and orthopedic issues makes it increasingly difficult to recommend traditional gonadectomy universally. Multiple studies have linked the following disorders to gonadectomy:
- Lymphosarcoma and hemangiosarcoma in female Golden Retrievers
- Cranial cruciate ligament disease in male and female Golden Retrievers, as well as in many large breeds
- Osteosarcoma in Rottweilers
- Urinary incontinence in medium to large-sized bitches
In general, in dog breeds that are prone to developing cancer and orthopedic diseases, gonadectomy likely increases the risk. Evidence also supports the relationship between neutering and the development of prostate cancer. For most conditions, the risk is higher when dogs are spayed and neutered at a younger age. The exceptions are lymphosarcoma and obesity, which are positively associated.
How to decide whether to spay or neuter your dog
An individualized decision-making process is recommended when deciding whether to spay or neuter your dog. Its breed, size, age, and disease risk profile are all important considerations. The research summarized in Romagnoli’s paper is helpful in making the decision.
The author emphasizes that currently, there’s not enough research to warrant abandoning spaying and neutering for all dogs. Many small breeds do not have the same risks of cancer and orthopedic problems as larger dogs. Additionally, the overall risk of a particular disease may be low (so that even an increase due to gonadectomy still results in a small overall risk).
Gonadectomy before puberty is currently not recommended in companion dogs regardless of breed, size, or other factors. Early spaying or neutering increases the risk of:
- urinary incontinence
- problems related to the incomplete development of the female’s vulva
- orthopedic disorders due to the delay of the growth plate closure
Gonadectomy should also not be used as a treatment for benign prostatic hyperplasia or behavioral problems.
What about hormone-sparing sterilization?
This scientific review supports the movement toward hormone-sparing sterilization (HSS), such as ovary-sparing spay (hysterectomy) for females and vasectomy for males. These procedures effectively prevent unwanted reproduction while maintaining the dog’s sex hormone production.
HSS mitigates the increased risks associated with hormone-related conditions like many cancers, orthopedic issues, and urinary incontinence. The paper notes that current research, including a study comparing HSS dogs, gonadectomized dogs, and sexually intact dogs, further supports the long-term health and positive behavioral outcomes of hormone preservation.
Veterinarians and pet owners should discuss the responsibilities of having a dog sterilized through HSS. This includes an understanding that the dog will behave like an intact dog (although it cannot reproduce). Regular health checks are also crucial for intact or HSS-sterilized dogs to detect mammary or prostatic conditions and ensure they’re diagnosed and treated at an early stage.
For more information about the health impacts of traditional spaying and neutering, as well as hormone-sparing sterilization, visit our hormone-sparing sterilization projects and articles.
