The Neutering Effect: How Long Until Testosterone Drops in Dogs?

For dog owners who want to know when their pet's hormones will change after a neutering procedure, one of the most important things to know is how long it takes for testosterone to decrease. In male dogs, testosterone decreases dramatically in the first 1-2 weeks after neutering as the body metabolizes the hormone, but it can take up to 6 weeks for testosterone to be fully metabolized.

Even though testosterone decreases immediately after the surgery, the biological impacts on the dog's body and behavior take longer to develop as the hormone is metabolized. This article will review veterinary and animal science research that has investigated how long it takes for testosterone to be depleted after neutering. It will also look at how long it takes for the changes in behavior and the reduction of certain health risks to occur after testosterone is no longer being produced.

How Neutering Affects Dog Behavior and Temperament

Neutering, or the surgical removal of a dog's reproductive organs, has a well-documented effect on dog behavior and temperament. Most of these changes are due to the reduction in testosterone, a hormone that plays a role in several behaviors in male dogs, including sexual behavior, aggression, and urine marking according to PetMD.

The most consistently observed changes in behavior after neutering are a reduction in mounting, roaming, urine marking, and some forms of aggression in male dogs. A study published in PMC showed that neutered male dogs had significantly reduced rates of mounting, pulling on the leash, and aggression toward their owners compared to before they were neutered.

That said, the effects of neutering on behavior are not always clear-cut. While some research has shown that neutering can reduce certain behaviors, other studies have shown the opposite. For example, an article in Veterinary Practice reported that neutering has been associated with an increase in anxiety, fearfulness, and resource guarding in some dogs. Neutered dogs have also been shown to be more emotionally unstable and have higher rates of aggression toward their owners.

The age at which a dog is neutered, particularly whether it occurs before or after puberty, may also affect the changes in behavior that occur after the procedure. A study cited by VCA Animal Hospitals found that neutering male dogs before puberty was associated with an increase in aggression toward strangers and other dogs, although more research is needed to confirm this finding. On the other hand, VCA Animal Hospitals reported that delaying neutering until after puberty was associated with an increase in trainability and a decrease in hyperactivity.

These studies show that the effects of neutering on dog behavior and temperament are complex and depend on a number of factors, including the dog's individual characteristics and the age at which they are neutered. Because of this, it's important for dog owners to keep an open mind and talk to their veterinarians before deciding to neuter their pets.

Potential Health Effects of Low Testosterone in Neutered Dogs

Neutered dogs are often left with extremely low testosterone levels, which can cause a number of issues. As noted in an article in the IVC Journal, loss of muscle mass, decreased mobility, and joint/spine issues are all common in neutered dogs with low testosterone. In fact, testosterone deficiency can make conditions like hip dysplasia, arthritis, and disc disease worse.

The article also notes that low testosterone can lead to obesity, anxiety, and other behavioral changes in some neutered dogs. A study highlighted by Phys.org showed that treating a neutered dog with Testosterone Replacement Therapy (TRT) to restore normal hormone levels helped the dog's mobility and energy levels. The therapy led to a significant increase in muscle mass and a decrease in limping and anxiety.

In addition to these potential health effects, testosterone replacement therapy can also be used to treat low testosterone levels in neutered dogs. As shown in a study in PubMed, surgical castration led to testosterone levels below 1.0 ng/mL in all dogs, while chemical sterilization led to more varied effects on testosterone. A veterinarian can help determine if TRT is a good option for treating the potential health effects of low testosterone in a neutered animal.

Hormone-Sparing Sterilization Procedures

If you're worried about the potential side effects of low testosterone in neutered dogs, there are sterilization procedures that can be performed while still allowing the dog to maintain their natural hormone levels. For female dogs, an ovary-sparing spay (hysterectomy) can sterilize while preserving the ovaries and their hormone production per the Parsemus Foundation. This procedure removes the uterus and cervix but leaves the ovaries, which means the dog will still go through heat cycles and produce hormones.

Similarly for male dogs, a vasectomy can sterilize while keeping the testicles and testosterone production intact per the AKC. This surgery involves cutting or clamping the vas deferens tubes to prevent the release of sperm, but it doesn't remove the testicles like a traditional neuter.

There are also other non-surgical methods that are still in the experimental phase, including epididymal injections that stop sperm production without affecting hormones per the IVC Journal. While these hormone-sparing sterilization procedures are intended to offer the benefits of sterilization without the potential drawbacks of hormone loss, they can also increase the risk of certain reproductive cancers and hormone-related behaviors, which pet owners should talk to their vet about.

Things to Think About for Pet Owners

If you're a pet owner thinking about neutering your dog, it's important to consider the potential pros and cons. Neutering is a popular and effective way to prevent overpopulation and lower the risk of certain health problems like reproductive cancers per PetMD. That said, pet owners should know that the decrease in testosterone that comes with neutering can have behavioral and health effects.

Talking to a vet can help you decide when the best time to neuter your dog is based on their specific needs and situation. VCA Animal Hospitals points out that neutering male dogs before they hit puberty may be associated with an increase in aggression, but more studies need to be done to confirm this. If you're worried about the effects of low testosterone, hormone-sparing procedures like vasectomies and ovary-sparing spays may be good options per the AKC.

No matter which sterilization option you choose, it's important to continue training, exercising, and watching your dog closely to make sure you can address any health or behavioral issues that may come up after they're neutered. Taking a proactive approach to your dog's care will help make sure they're healthy and happy throughout all stages of their life.

Conclusion: Weighing the Benefits and Drawbacks of Neutering

Neutering has been shown to have a number of effects on a dog's behavior and temperament. The most well-documented of these is the reduction in testosterone, which has been shown to impact a number of behaviors in male dogs, including sexual behavior, aggression, and urine marking.

The most consistent effects of neutering have been a reduction in mounting, roaming, urine marking, and some forms of aggression in male dogs. A study published in PMC showed that neutered male dogs had a reduction in mounting, pulling on the leash, and owner-directed aggression after being neutered.

That said, the effects of neutering on behavior are not always predictable or consistent. While some studies have shown that neutering can reduce undesirable behaviors, others have shown the opposite. According to an article in Veterinary Practice, neutering has been shown to lead to an increase in anxiety, fearfulness, and resource guarding in some dogs. In addition, neutered dogs were more likely to show emotionally unstable behavior and owner-directed aggression.

In addition, when a dog is neutered can also impact the effects of the procedure on behavior. A study cited by VCA Animal Hospitals found that neutering male dogs before puberty was associated with an increase in aggression toward strangers and other dogs, although more research is needed. On the other hand, delaying neutering until after puberty was associated with an increase in trainability and a decrease in hyperactivity, according to the same source.

These studies show that the effects of neutering on a dog's behavior and temperament are complex and depend on a number of factors, including when the dog is neutered. As a result, it's important for dog owners to keep an open mind and talk to veterinarians before making a decision about whether to neuter their dogs.