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Should I Neuter My Dog? The Shocking Risks Of Neutering Early

Intact male dogs tend to live longer healthier lives
Image: Courtesy of
Images of frightened, discarded cats and dogs in shelters tug at our hearts and serve to encourage the public to embrace the spaying and neutering of pets as a way to reduce the unwanted pet population. 

The burgeoning population of abandoned cats and dogs has increased in tough economic times. A growing trend in the animal welfare and rescue community has been to spay and neuter cats and dogs prior to releasing their charges to their new adoptive families.  

In the case of young kittens and puppies, some of the more zealous of these organizations have begun spaying and neutering puppies as early as 6 -8 weeks of age.  

Research regarding the long term benefits and risks that such early intervention may have on the physical development of the adult dog is many years away. However we can look to existing research for the effects on the health of dogs spayed or neutered prior to one year of age.  The surprising results of these studies inform the advisability of altering male dogs as well as the age that spay or neuter may be appropriate.

In 2007, Laura J. Sanborn, M.S. published a study, “Long-Term Health Risks and Benefits Associated with Spay / Neuter in Dogs.”  This study reviewed much of the existing veterinary medical literature, over 50 peer-reviewed articles, in an attempt to access the health impacts of spaying and neutering dogs, and to aid veterinary care providers and pet owners in making more informed decisions regarding the advisability of spay / neuter as well as appropriate timing in the dog’s development for surgery.

The Health Benefits and Risks of Neutered Male Dogs

Veterinarians regularly tout the health benefits associated with neutering male puppies.  Reduction of prostate cancer is frequently cited as a benefit, additionally prevention of testicular cancer is also cited as an important consideration in the long term health of the dog.  While neutering will eliminate the risk of dying from testicular cancer, the risk of developing this cancer and dying from it, for an intact dog, is less than one percent. And while prostate cancer in humans is linked to testosterone, studies show that in canines it appears to have an opposite effect on them than it does on humans.

Benefits of neutering found in a review of the medical studies included moderate reduction in the likelihood of males developing:
  • perianal fistulas
  • non-cancerous prostate disorders
  • and possibly a reduction in the risk of developing diabetes
While the benefits associated with neutering males in this study appear minimal, the increased risk of developing several cancers, obesity, orthopedic disorders and adverse reactions to vaccinations is substantial.

Risks: Neutered Male Dogs vs. Intact Males:
  • Neutered males are 1.6 times more likely to develop Cardiac Hemangiosarcoma than their intact counter parts.
  • Are twice as likely to develop Urinary Tract Cancer than intact males
  • Are four times more likely to develop Prostate Cancer than intact males.
  • Experience a 27% increase in adverse reactions to vaccinations over their intact counterparts.
  • And if neutering is done prior to 1 year of age, it substantially increases the risk of the more common cancer Osteosarcoma (bone cancer)
Additionally, neutered dogs are 4 times more likely to be obese than their intact counterparts, in fact neutering triples the risks of hypothyroidism, which causes weight gain, lethargy and hair loss.  

Perhaps due to being overweight, neutered dogs also experience a higher risk of developing orthopedic disorders and are at greater risk for progressive geriatric cognitive impairment.

Weighing the benefits against the increased health risks associated with neutering male dogs, it appears from this study that the risks far outweigh the benefits, with one major exception. Unilateral and bilateral cryptorchism, or undescended testicles,when not neutered, results in a 13 times greater chance of developing testicular cancer.  While prognosis for treatment of testicular cancer is good, a 90% cure rate, it is advisable to neuter these dogs. 

Marking behavior normally occurs when 
there are intact females in the home
 Courtesy of

Marking Indoors

Many owners wish to eliminate the tendency of male dogs to mark territory, by neutering males before they reach sexual maturity.  In fact males neutered around 6 months of age frequently never learn to “hike” their legs, and eliminate in the same manner as puppies and female dogs do. 

However, with proper training, males will learn not to mark or hike their legs indoors.  It is only when males are exposed to intact females and their estrus cycle, that the male marking behavior becomes a challenge inside the home.

Aggression Reduction

Another reason cited for neutering males is to reduce or eliminate aggressive behavior. Intact dogs are not welcome at dog parks and for good reason.  A pair of intact males presented with an intact female in estrus will likely result in a display of aggression between the males. 

Dominant males will want to assert themselves, and the cost to your dog's health and your wallet are not worth the risk.  If you are keeping an intact male dog, respect the rules of dog parks and most municipal and county laws. Keep your dog on leash or confined at all times.

Total Lifespan Intact vs. Neutered Males

In a recent study at University of Georgia, researchers examined records of over 40,000 dogs to determine whether intact males or neutered males live longer.  While they too found that neutered males tend to die of certain cancers at a higher rate than their intact counterparts, overall the neutered dogs had, on average, a longer lifespan.  The study showed that intact males and females tended to die more frequently of infectious disease at an earlier age than the spayed and neutered dogs in the study.

It should be noted that the dogs in this study were from teaching hospitals, and the results might be different in private veterinary practices.  It is not known whether the intact males and females were pets or strays and what level of care they had received prior to admission. 

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Should We Neuter Our Dog?

If you have a breed that is predisposed to developing certain cancers such as osteosarcoma, lymphoma or hemangiosarcomo, and you have a well fenced yard, you may want to leave your male intact.  

The research clearly shows that the earlier that you spay or neuter your pet, they greater the risk is of developing one of the aforementioned cancers.

However, recent research also suggests that neutered males live longer than intact males. If you opt for neutering, we suggest that you wait until your dog’s first birthday to alter him.  While many vets advocate neutering at 6 months, it appears that hormones from the reproductive system are aiding in the development of the dog’s autoimmune system. Allowing him to reach sexual maturity will give him the advantage that these hormones provide, and hopefully extend his lifespan as well as the quality of his final years.

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