Neutering, behavior and health impact, inherited disorders, misc

  • In another thread I mentioned issues of behavior when dogs are neutered. That lead me to several links, some behavior related, some health. Just sharing them here:

    Just going to post the links:

    1. Results—Dogs gonadectomized at ≤ 6 months, between 7 and 12 months, or at > 12
      months of age had significantly increased odds of developing mast cell cancer, lymphoma,
      all other cancers, all cancers combined, and fear of storms, compared with the odds for sexually
      intact dogs. Females gonadectomized at ≤ 12 months of age and males and females
      gonadectomized at > 12 months of age had significantly increased odds of developing
      hemangiosarcoma, compared with the odds for sexually intact dogs. Dogs gonadectomized
      at ≤ 6 months of age had significantly increased odds of developing a behavioral disorder.
      The younger the age at gonadectomy, the earlier the mean age at diagnosis of mast cell
      cancer, cancers other than mast cell, hemangiosarcoma, lymphoma, all cancers combined,
      a behavioral disorder, or fear of storms

    • Dogs neutered or spayed at any age were at significantly increased risk for developing mast cell cancer, lymphoma, all other cancers, all cancers combined, and fear of storms, compared with intact dogs.
    • Females spayed at 12 months or younger, and both genders neutered or spayed at over 12 months had significantly increased odds of developing hemangiosarcoma, compared with intact dogs.
    • Dogs of both genders neutered or spayed at 6 months or younger had significantly increased odds of developing a behavioral disorder, including separation anxiety, noise phobia, timidity, excitability, submissive urination, aggression, hyperactivity and/or fear biting.
    • The younger the age at neutering, the earlier the age at diagnosis with mast cell cancer, cancers other than mast cell, hemangiosarcoma, lymphoma, a behavioral disorder, or fear of storms.
    • Compared to intact dogs, neutered and spayed dogs had a 3.5 times higher risk of developing mast cell cancer, regardless of what age they were neutered.
    • Spayed females had nine times higher incidence of hemangiosarcoma compared to intact females, regardless of when spaying was performed, however, no difference in incidence of this type of cancer was found for neutered vs. intact males.
    • Neutered and spayed dogs had 4.3 times higher incidence of lymphoma (lymphosarcoma), regardless of age at time of neutering.
    • Neutered and spayed dogs had five times higher incidence of other types of cancer, regardless of age of neutering.
    • Spayed females had 6.5 times higher incidence of all cancers combined compared to intact females, and neutered males had 3.6 times higher incidence than intact males.

    Similar studies have been conducted on Rottweilers and Golden Retrievers, both yielding similar results.

    Another study conducted in 2009, compared the medical histories, ages and causes of death of 119 Rottweilers with above-average longevity of at least 13 years and 186 Rottweilers with an average longevity of about 9 years (…/j.1474-9726.2009.00513…/pdf). When speaking about the results, David J. Waters, Associate Director of Purdue University’s Center on Aging and the Life Course and a Professor in the Department of Clinical Sciences, stated:

    “Like women, female dogs in our study had a distinct survival advantage over males. But taking away ovaries during the first four years of life completely erased the female survival advantage. We found that female Rottweilers that kept their ovaries for at least six years were four times more likely to reach exceptional longevity compared to females who had the shortest lifetime ovary exposure."

    Further, it has been widely reported by numerous veterinarians that early spay/neuter not only causes osteosarcoma in large breeds but also affects growth rate and skeletal development because sex hormones are known to influence the maintenance of the skeletal structure and mass.

    In “Endogenous gonadal hormone exposure and bone sarcoma risk,” written by the Department of Veterinary Clinical Sciences at Purdue University, and published in Cancer Epidemiology Biomarkers Prev., 2002 Nov, pp. 1434-40 (, it was held that:

    “Risk for bone sarcoma was significantly influenced by age at gonadectomy. Male and female dogs that underwent gonadectomy before 1 year of age had an approximate one in four lifetime risk for bone sarcoma and were significantly more likely to develop bone sarcoma than dogs that were sexually intact.”

    In 2007, Laura J. Sanborn, M.S., wrote a scholarly treatise entitled “Long-Term Health Risks and Benefits Associated with Spay/Neuter in Dogs which can be found here:…/LongTermHealthEffectsOfSpayNeut…. Ms. Sanborn reviewed more than 50 peer-reviewed papers and found that spay/neuter increases the risk of osteosarcoma, hemangiosarcoma, hypothyroidism and other less frequently occurring diseases associated with neutering male dogs. As Larry S. Katz, Ph.D., Associate Professor and Chair of Animal Sciences at Rutgers University stated in the treatise’s introduction: “It would be irresponsible of the veterinary profession and the pet owning community to fail to weigh the relative costs and benefits of neutering on the animal’s health and well-being. The decision for females may be more complex, further emphasizing the need for individualized veterinary medical decisions, not standard operating procedures for all patients.”

    More published studies on both dogs and cats, which are too numerous to mention, are referenced in a white paper written by The Society for Theriogenology on pages 3-12 (…/SocietyForTheriogenologyMandato…). This white paper discusses the many considerations that should be made regarding pet sterilization and the reasons why mandatory spay/neuter regulations are not in the best interest of the health or well-being of pets.

    1. Interesting articles on neutering and behavior. (some same material but I found the vet's comments worth reading)

    It was interesting to read. I had a few flame me for posting, said I was encouraging indiscriminate breeding, etc (not here, my home wall). But I found other research backing it up. I of course, had read about bitches spayed during "wrong" time of heat cycle increasing aggression long ago. But the issue of cancer with neutering is what had me keep my "already very high rates of bone cancer" Rottweilers intact.


    1. Dr Laura, a long time friend, wrote me long ago about the need for waiting a couple of cycles with bitches who were very aggressive as pups.

    Since dogs' ovaries are inactive much of the year, they generally show less detriment from lack of estrogen than people, who have constantly cycling ovaries. The only research I have seen, and I haven't seen original papers, just what is quoted from Dr. Karen Overall, is that female dogs who are dominant aggressive before they go into heat may show some reduction, or at least less progression, by going through one or two heat cycles. The current theory is that these super-dominant females were androgenized by contact with the hormones of a male pup during gestation; on rare occasions when their placentas develop some communication. those with retained ovaries will have no protection from breast cancer, will continue to cycle and create an attractive nuisance with male dogs, and are at risk for a stump pyo on the bit of remaining uterus near the cervix. The only benefit in that case would be pregnancy prevention. And, every dog I spayed who was aggressive during the heat only went to their normally sweet diestrus selves.

    Laura Cook dvm<<

    1.       "Spaying and neutering of dogs is a well-accepted procedure in the United States and has many positive effects on behavior, health, and longevity. Although recent reports suggest that spaying and neutering may increase the occurrence of some joint disorders and some cancers, the relationship between inherited diseases and spay/neuter status has not fully been explored. The present study evaluated the prevalence and risk of genetic diseases, both early and late onset, in intact and neutered male and female dogs that were seen over a 15-year period at a university teaching hospital. Spayed and neutered dogs were at less risk for early and congenital conditions (aortic stenosis, early onset cataracts, mitral valve disease, patent ductus arteriosus, portosystemic shunt, and ventricular septal defect) than intact dogs. Neutered male dogs were at less risk for bloat (gastric dilatation volvulus) and dilated cardiomyopathy, whereas spayed females were at increased risk for intervertebral disk disease. Spaying or neutering in both sexes was significantly associated with an increased risk for cancers (hemangiosarcoma, hyperadrenocorticism, lymphoma, mast cell tumor, and osteosarcoma), ruptured anterior cruciate ligament, and epilepsy. For elbow dysplasia, hip dysplasia, lens luxation, and patellar luxation neutering had no significant effect on the risk for those conditions. A dog that was spayed or neutered was associated with a reduced risk of vehicular injury, a condition chosen as a control. The complexity of the interactions between spaying/neutering and inherited conditions underscores the need for reflective consultation between the client and the clinician when considering the procedure. The convenience and advantages of spaying or neutering dogs that will not be included in a breeding program must be weighed against possible risk associated with the procedure. Additionally, if owners elect to keep their dogs intact, they must then assume responsibility to vigilantly guard against unplanned litters."

    Correlation of neuter status and expression of heritable disorders
    Gonadectomy, or neutering, is a very common surgery for dogs having many positive effects on behavior, health, and longevity. There are also certain…


    1. Debra Levey: It took me a bit to come back to this (we are moving to Israel).

    Anyway... with the diseases listed... it makes sense. Think about humans and their different levels of heart disease between genders even with other factors weighed. Those pesky hormones.

    The problem is that we always see articles here that say that neutering animals kills them, that compared to us, UK or European dogs live longer thing. While I have seen it said, but have yet to find a valid study. I have looked at life expectancy in breed clubs in the US and UK etc... they are the same. If there is a study not only showing they live longer, but any clue on why, I'd like to see it.

    However, this study concentrates on dogs here and the spay/neuter life expectancy issue, including the belief here in the US by many that neutering causes more cancer. The study brings up that increase in cancer may be nothing more than the fact they actually live longer, not less.

    We found that sterilization significantly affected survival in both males ( = 446, P<10−6) and females ( = 1372, P<10−6) (Figure 1A). Sterilization increased life expectancy by 13.8% in males and 26.3% in females among the FC dogs.

    It's a really interesting article.

    Reproductive Capability Is Associated with Lifespan and Cause of Death in…


    Notes from discussion with Professor Catchpole at Crufts, where he went through the attached presentation with me:
    The first slide shows a beta cell - this is the cell type that produces insulin when it detects glucose. Beta cells are present in the pancreas. If you look at the top of the cell, you can see glucose entering the cell. The entry of glucose into the cell triggers insulin production (the brown circles represent insulin being secreted from the cell). Along the sides, you can see "incretin mimetics", "amylin analogues" etc. - these are various medicines that are used to treat diabetes.
    If you look at the bottom of the cell, the secretion of insulin from the beta cell is accompanied by the release of other molecules, namely IAPP and C-peptide. Catchpole is interested in IAPP in particular. Normally, IAPP is simply degraded after its release from the cell. However, sometimes, IAPP, instead of degrading, forms aggregates. These aggregates trigger a signal that leads to destruction and loss of beta cells, leading to reduced insulin production and therefore diabetes.
    This slide explains beta cell renewal in the pancreas. Old beta cells are continuously being destroyed by degeneration (via a form of cell death known as apoptosis), and replaced by regeneration (from stem cells) of new beta cells. In a healthy animal, this process is balanced so that the number of beta cells is always kept at an optimal number for normal insulin production.
    You can see that a rise in blood glucose (aka hyperglycemia) leads to the production of insulin, and the other two compounds IAPP and C-peptide.
    This slide shows the situation in Samoyeds. In our breed, there is a higher risk of the rate of beta cell destruction exceeding that of beta cell formation. Therefore, there is an overall loss of beta cells, leading to insulin deficiency and diabetes.
    The reason for this elevated risk in our breed is not known. However, potential contributors are shown in red. Among these, there are genetic factors, which may be reduced by not breeding from dogs with diabetes. Metabolic factors, such as hormone antagonism which can be eliminated by spaying, and so on.
    This slide shows the situation in Boxers, the breed Catchpole wants to compare Samoyeds against. In Boxers, the balance is skewed in the opposite direction - the rate of beta cell production tends to exceed that of beta cell loss, often leading to overproduction of beta cells. In the best case scenario, this means minimal diabetes risk in Boxers. In the worst case scenarion, this breed is actually prone to developing insulinomas when the production of beta cells becomes uncontrolled.

    I am not sure this file can be seen. Glad to copy it if interested: beta cell biology and pathogenesis of diabetes.pdf?token=AWzFYggWyuqaCw0UH8VX3uHQDrzcKd3vK5_mOcYUvXzlBZ8wHEAXuxTGIYaZkAjafjUrXMD1G5yRT74r-MCd4r0lukYnw6ZMjDtWXXiIMeFubVnlWSxb36eZaeNE0B15aWKtzhUG28ejPV6FrND1MB7L


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