Neutering is the process of surgically removing the testicles of a male cat in order to sterilize them and prevent reproduction. It is a very common practice, with studies estimating that 80% of pet cats in the US are neutered.
After neutering, the testosterone levels in a cat’s body will start to decline. However, testosterone does not immediately disappear from their system. It can take weeks or months for hormone levels to fully dissipate. Understanding this process can help cat owners know what to expect after neutering in terms of their cat’s behavior and health.
This information is useful for cat owners because the changes in testosterone levels impact the cat’s activity level, urge to roam and fight, and the risk of certain diseases. Knowing how long testosterone persists gives owners insight into when they can expect to see these changes after neutering.
Testosterone Production in Cats
In male cats, testosterone is primarily produced in the testes. The testes produce testosterone starting around 4-6 weeks of age, which then impacts male development and behavior. Higher levels of testosterone lead to the development of male physical characteristics like larger size, muscular body, broad head, and external genitalia. It also drives male-typical behaviors like territorial marking, roaming, aggression, and sexual behavior. Intact male cats tend to urine mark more frequently, fight with other cats, have a stronger odor, and display mating behaviors compared to neutered males. According to PetMD, testosterone levels peak at around 10-12 months of age in cats.
The Neutering Procedure
Neutering, also known as castration, refers to the surgical procedure of removing a male cat’s testicles. This involves general anesthesia and surgical removal of both testicles, which are located inside the scrotum (VCA Hospitals, 2022)[1]. By removing the testes, the source of testosterone production is eliminated. Without testes, the cat can no longer produce testosterone on its own (Cornell University, 2022)[2].
[1] https://vcahospitals.com/know-your-pet/neutering-in-cats
[2] https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/spaying-and-neutering
Testosterone Levels Right After Neutering
Testosterone levels in male cats drop quickly after neutering surgery, although some amount of the hormone is still present immediately after the procedure. According to a study by Johnstone et al. (1984), testosterone levels decreased by 50-60% within 2 hours after neutering. However, testosterone does not immediately disappear from the cat’s system.
After surgery, the remaining testes tissue and cells will continue to produce small amounts of testosterone for a short time. Additionally, the hormone has likely accumulated in the cat’s body over months and years prior to neutering. Therefore, while levels drop significantly right after neutering, low concentrations of testosterone can persist for 1-2 weeks as the residual amount is metabolized and excreted from the body.
It takes additional time for this residual testosterone to fully leave the cat’s system. Neutering rapidly curtails testosterone production, but does not eliminate the hormone overnight. Owners must be patient as their cat’s body adjusts post-surgery.
When Does Behavior Change Occur?
According to https://www.thewildest.com/cat-behavior/male-cat-behavior-after-neutering, aggression and marking behaviors like urine spraying may decrease within days or weeks after neutering.
However, some undesirable behaviors can take longer to diminish. As the VCA Animal Hospital states, “The maximum benefit will be seen 8 to 12 months after castration.” While testosterone levels drop rapidly after neutering, it takes time for some of the effects of early exposure to wear off.
Territorialism, roaming, howling, and some types of aggression often persist longer than marking behaviors. But over time, neutered cats tend to become calmer, friendlier, and more docile. The length of time for behavior changes varies per cat and depends on factors like age at neutering.
Complete Elimination of Testosterone
While some behavioral changes due to neutering may appear within the first 1-2 weeks, it can take 4-6 weeks for a cat’s testosterone levels to become completely undetectable after being neutered according to Neutering Male Cats: Behavior and Recovery Guide. This length of time is required for the remaining testosterone to fully metabolize and exit the body.
By the 4-6 week mark post-neutering, testosterone is essentially gone from a cat’s system. As a result, all testosterone-related behaviors and impacts have been eliminated by this time. These include spraying urine, roaming/escaping, aggression, and sexual behaviors. The cat’s personality has fully stabilized into its long-term post-neutered state.
Persistent Effects of Early Testosterone
Although neutering removes the main source of testosterone, it does not reverse developmental changes that occurred under its influence during puberty and young adulthood (prior to neutering).[1] For example, bone structure, vocal cord size, muscle mass and coat thickness are permanently masculinized by early testosterone exposure.[1],[2] This gives neutered male cats a more masculine body and voice compared to females. However, while these effects cannot be reversed, neutering does prevent any further masculinizing changes from occurring.
In summary, developmental effects of testosterone prior to neutering will remain, but the procedure stops continued masculinization. So the sooner a male kitten is neutered, the more feminized they will be as an adult cat.
Risks If Neutering Is Delayed
Postponing a cat’s neutering procedure to 6 months of age or later can pose some risks. As testosterone levels remain elevated in an intact cat beyond 6 months, problematic behaviors may develop or worsen.
Cats neutered after 12 months of age are more likely to retain behaviors like aggression, territorial marking and urine spraying inside the home, roaming and fighting with other cats, and sexual behaviors like mounting and yowling. These habits can become deeply ingrained by 18-24 months, making an older cat’s behavior more difficult to modify after neutering.
There are also health risks to delaying neutering. Testicular cancer is more prevalent in intact cats, especially over the age of 10. Intact males are at higher risk for prostatic diseases as they age, as well as certain tumors of the reproductive system like Sertoli cell tumors. Serious infections of the prostate or testicles are also more likely in unneutered male cats.
For optimal lifelong health and behavior, veterinarians widely recommend neutering cats around 6 months of age before testosterone-driven behaviors have an opportunity to develop.
The Bottom Line
In summary, it takes around 2-4 weeks for testosterone levels to significantly drop after a cat is neutered. However, the behaviors associated with testosterone may take 1-2 months to fully dissipate. This is because early testosterone exposure can have lasting effects on the brain and behavior.
It’s highly recommended to neuter a male cat before 6 months of age. Neutering at an early age (4-6 months) prevents testosterone from influencing development and leads to the best behavior outcomes. If neutering is delayed past 6 months, the cat will be more likely to retain behaviors like urine marking, aggression, roaming, and sexual urges. Early neutering also reduces the risks of prostate issues and some cancers later in life.
References/Further Reading
List sources consulted in writing this article:
Neutering the Male Cat. Mar Vista Animal Medical Center. https://www.marvistavet.com/neutering-the-male-cat.pml
Neutering Male Cats: Behavior and Recovery Guide. The Wildest. https://www.thewildest.com/cat-behavior/male-cat-behavior-after-neutering
Allaway, D., Gilham, M., Colyer, A., Morris, P. J., & Butterwick, R. (2016). Metabolic profiling reveals effects of age, sexual development and neutering in plasma of young male cats. PloS one, 11(8), e0160164. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5152928/
Suggest additional resources on the topic:
– ASPCA’s article on neutering cats: https://www.aspca.org/pet-care/general-pet-care/spayneuter-your-pet
– Your local veterinarian’s website may have helpful information on neutering cats
– PetMD’s article on neutering cats: https://www.petmd.com/cat/care/evr_ct_neutering_spaying
– Additional scholarly articles and studies on PubMed related to neutering cats and testosterone levels