It is becoming a well-known fact, in the dog community, that early spay and neuter can lead to many health problems later in life.
But a new study out of Oregon State University is shining a light on the procedure itself and the inherent dangers associated with traditional sterilization.
Gonadectomy is the process of removing the testes or ovaries, and for our purposes(and the study’s), will be used to refer both to spay and neuter. The paper explains that, in a normal adult mammal, the gonads function as a regulatory hub for the hormone testosterone, in males, and estrogen, in females. But in an adult mammal, that has been sterilized via gonadectomy, this process is interrupted, leading to a 30 fold increased concentration of Luteinizing hormone(LH), a pivotal component of the system of regulation.
The authors go on to show that, while most LH receptors are in the reproductive system, there are many that exist outside of it and the increased concentrations resulting from sterilization in this manner may cause increased risk for various health and behavioral issues.
The researchers discuss the adverse effects of gonadectomy, such as increased obesity, development of urinary calculi(solid particles), increased risk of diabetes development, urinary incontinence, increased risk for cranial cruciate ligament rupture, hip dysplasia, and a host of other physiological issues.
All of these conditions are shown to be, at least somewhat, reliant on the LH hormone.
One of the most interesting conclusions of this study is the effect that gonadectomy and the subsequent super concentration of LH have on the behavior of the dog.
The study concedes that the research on this subject has come down on both sides of the fence. Some seem to find that behavior problems improve while others find that sterilization causes an increase or worsening problematic behavior.
They cite the specific example of “reproductive-related behavior” such as mounting, marking, etc being reduced in dogs that have been sterilized. But go on to feature a host of problems related to gonadectomy, which include increased aggression and fear.
The behavior that is mentioned as becoming more problematic both find their origins in the part of the brain called the hippocampus and hypothalamus which have an abundant amount of non-reproductive system LH receptors. The authors posit that the changes in the fear and aggression levels in dogs, post-sterilization, may be the result of the increased concentrations of LH in these parts of the brain.
The study concludes that “canine gonads are no merely reproductive organs but critical to endocrine, musculoskeletal, behavior, and anti-neoplastic health” and, as a result, “a surgical sterilization method that enables the dog to keep gonads intact while still preventing reproduction is likely to prolong its health”