This month, I’d like to share with you a study on spay and neuter procedures
that’s making big waves in veterinary circles. It really has surprised many
people. However, before I launch into the review, I want to caution you that
sometimes studies can be misleading, so let’s take the following with a grain of
salt before we overhaul the way we think about the importance of alteration
This new study was published by researchers at the University of California –
Davis. It indicates that neutering may adversely impact the risk of some dogs
for developing certain cancers and joint problems. This study runs counter to
prevailing sentiments, so it’s worth a review of where we stand now.
In the U.S., pet parents overwhelmingly support the neutering of dogs, justified
by concerns about overpopulation and minimizing the development of unwanted
behaviors (such as roaming, aggression and marking). Nowadays, neutering is
considered part of responsible pet care, and spay and neuter surgeries are
usually done when dogs are less than one-year-old.
But in the past 10 years, studies have indicated that neutering can have
negative health effects for certain breeds (see references). Drawing on these
previous studies, researchers at Davis used historical data from their
veterinary hospital to examine the effects of neutering on the risks of several
diseases in one breed, the Golden Retriever. The researchers involved chose to
focus exclusively on Goldens due to their popularity in the U.S. and Europe, as
well as their predisposition to certain genetic issues. The study focused on
joint disorders and cancers because neutering removes sex organs (testes or
ovaries), which interrupts the production of certain hormones that play
important roles in key body processes (such as the closure of bone growth
The study showed that in Golden Retrievers, the rates of hip dysplasia,
cranial cruciate ligament tear (knee injury), lymphosarcoma, hemangiosarcoma and
mast cell tumors were higher in both males and females that were neutered
compared to intact (non-neutered) retrievers. Specifically, early neutering was
associated with an increase in the occurrence of hip dysplasia, cranial cruciate
ligament tears and lymphosarcoma in males, and cranial cruciate ligament tears
in females. In fact, there was a doubling of the incidence of hip dysplasia
among early-neutered males.
Another interesting finding was that late neutering (after the first heat
cycle) in females was associated with a higher incidence of mast cell tumors and
hemangiosarcomas, with no apparent explanation. In contrast to the rather strong
evidence for neutering males and/or females as a risk factor for certain cancers
and joint disorders, evidence for neutering as protection against a dog
acquiring one or more cancers is weak. The most frequently mentioned is mammary
cancer, however, a recent systematic review of published work on neutering and
mammary tumors found the evidence that neutering reduces the risk of mammary
neoplasia to be weak, at best (Beauvais W, Cardwell JM, Brodbelt DC, 2012).
Even given the results of this new study, the relationship between neutering
and disease-risk remains a very complex issue. For example, the increased
incidence of joint disease seen in early neutered dogs is likely a combination
of the effect on the growth plates and the increase in weight on the joints that
is commonly seen in neutered dogs, and may even be affected by genetic factors
yet to be determined. Obviously, more research is needed in this arena.
This research is notable for a couple of reasons. In Goldens, it suggests
that the neutering of males well post-puberty could possibly help to avoid the
problems of increased rates of hip dysplasia, cranial cruciate ligament tears
and lymphosarcoma. For females, the issue is more convoluted and more studies
are needed, because early neutering seems to increase the incidence rate of
cranial cruciate ligament tears and late neutering may be tied to higher rates
of certain cancers. For pet parents of pure-bred Goldens, the bottom line is
that it is extremely important to gather all information before deciding if and
when to neuter. As with all medical decisions, please review the options
available to your companion animal with your veterinarian before deciding on a
course of action.
It is important to note that the results of this study are breed-specific to
Golden Retrievers and cannot be extrapolated to other breeds, or dogs generally.
This study may or may not be the tip of an iceberg, as a full understanding of
the disease conditions affected by neutering across all breeds would require
many more breed-specific studies, and these may not bear any meaningful fruit.
Needless to say, veterinarians will be following new research closely.
Pet parents wanting to learn more about this provocative study can read it at
the link below (first listing under ‘References’).
Just to be absolutely clear, I am still very much committed to neutering pets
at a young age (although perhaps not the very young) due to the systemic problem
of overpopulation and the horrible consequences of doing nothing at all to turn
Thank you for all you do to make the world a better place for companion animals.
Dr. Jane Bicks
Torres de la Riva G, Hart BL, Farver TB, Oberbauer AM, Messam LL, Willits N,
Hart LA. Neutering dogs: effects on joint disorders and cancers in golden
retrievers. PLoS One. 2013;8(2):e55937. doi: 10.1371/journal.pone.0055937. Epub
2013 Feb 13.
Ru G, Terracini B, Glickman LT (1998) Host related risk factors for canine
osteosarcoma. Vet J 156: 31–39. doi: 10.1016/S1090-0233(98)80059-2.
Cooley DM, Beranek BC, Schlittler DL, Glickman MW, Glickman LT, et al. (2002)
Endogenous gonadal hormone exposure and bone sarcoma risk. Cancer Epidemiol
Biomarkers Prevent 11: 1434–1440.
Ware WA, Hopper DL (1999) Cardiac tumors in dogs: 1982–1995. J Vet Intern Med
13: 95–103. doi: 10.1892/0891-6640(1999)013<0095:CTID>2.3.CO;2
Prymak C, McKee LJ, Goldschmidt MH, Glickman LT (1988) Epidemiologic, clinical,
pathologic, and prognostic characteristics of splenic hemangiosarcoma and
splenic hematoma in dogs: 217 cases (1985). J Am Vet Med Assoc 193: 706–712.
Teske E, Naan EC, van Dijk E, Van Garderen E, Schalken JA (2002) Canine
prostate carcinoma: epidemiological evidence of an increased risk in castrated
dogs. Mol Cell Endocrinol 197: 251–255. doi: 10.1016/S0303-7207(02)00261-7
Villamil JA, Henry CJ, Hahn AW, Bryan JN, Tyler JW, et al. (2009) Hormonal
and sex impact on the epidemiology of canine lymphoma. J Cancer Epidemiol 2009:
Root Kustritz MV (2007) Determining the optimal age for gonadectomy of dogs
and cats. J Am Vet Med Assoc 231: 1665–1675. doi: 10.2460/javma.231.11.1665.
Beauvais W, Cardwell JM, Brodbelt DC (2012) The effect of neutering on the
risk of mammary tumours in dogs – a systematic review. J Small Anim Pract 53:
314–322. doi: 10.1111/j.1748-5827.2011.01220.x.