Health problems after hormone loss in dogs

Our understanding of the health impacts of spay and neuter started with research evaluating dogs that had their sex organs removed (called gonadectomy) at a very young age. In 2007, a respected veterinarian named Margaret Root Kustritz published a review of spaying and neutering dogs and cats at different ages. This generated a lot of discussion and further research reporting positive and negative health consequences of gonadectomy that vary by age, gender, and breed.

Today there is mounting evidence that the health benefits of keeping the sex organs in dogs may outweigh the health risks. A key 2013 publication from the University of California, Davis reported that the rates of two joint disorders and three cancers in Golden Retrievers were significantly higher in both males and females that were neutered early or late compared with intact (non-neutered) dogs. Many other studies have followed. For example, a 2014 study indicated that gonadectomized Vizslas had significantly increased odds of developing mast cell cancer, lymphoma, all other cancers, and fear of storms compared with the odds for sexually intact dogs. Brain tumors are also 11 times more likely in spayed than intact females. On the positive side, since dogs who have been spayed or neutered no longer have sex organs, they don’t get diseases associated with sex organs or hormones.

There is also evidence that it is the loss of hormones from spaying and neutering dogs that is causing an increased risk of long-term health problems. A study by Zink and colleagues reported that intact dogs and those sterilized with hormone-sparing procedures (vasectomy or hysterectomy) had reduced risk of general health problems and both problematic and nuisance behaviors as compared to spayed or neutered dogs.

Whether your dog might have health problems following spay or neuter depends on many factors, including the breed, sex, age of sterilization, and body size. Follow-up studies from the University of California, Davis have reported risk profiles of 35 breeds and mixed breed dogs, providing important information for veterinarians and pet-owners when considering sterilization. If you are considering sterilization options for your dog, consult with an experienced veterinarian to discuss the risks and benefits for your dog. And be sure to consider hormone-sparing sterilization procedures in your assessment. The following table summarizes our current knowledge of potential positive and negative health impacts. 

Summary of health impacts of spaying and neutering (gonadectomy):