To Neuter or Not to Neuter...

(This blog originally posted on 2/25/2006)

. . . the other side of the question.

"Just the facts, Ma'am."

Okeydokey!
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http://www.showdogsupersite.com/kenlclub/breedvet/neutr.html
It is no longer medically justifiable to castrate dogs for prevention of cancer. Castration predisposes to highly malignant prostatic cancer. Nearly all dogs afflicted with this nasty tumor are neutered individuals. Spaying helps to reduce the incidence of mammary tumors, if performed before the first heat. It does not eliminate the possibility, but does statistically reduce the risk. So, however, does lactation, as in humans.
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http://cebp.aacrjournals.org/cgi/content/full/11/11/1434
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.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12578741
Similar to confined socialized cats, feral cats gained significant weight and body fat after neutering.
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http://www.woodhavenlabs.com/ins-outs.html
Puppies who get frequent puppy vaginitis or bladder infections and have an "Innie" vulva should NOT be spayed before their first heat.
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http://www.jaaha.org/cgi/reprint/40/1/2-a.pdf
There is no indication to perform an ovariohysterectomy in healthy, nongravid\r\nbitches.1,2 Since many of the complications seen with ovariohysterectomies can be attributed to the cervical stump and the transection of the broad ligament,3,4 many now advocate ovariectomy as the procedure of choice for the sterilization of female dogs.
[Ms. X notes that an “ovariectomy” procedure simply removes the ovaries, leaving the uterus intact in the dog.]
More on Ovariectomy: http://www.vetcontact.de/en/art.php?a=81&t
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11439769&query_hl=2&itool=pubmed_docsum
Results suggest that the presence of circulating testosterone in aging sexually intact male dogs may slow the progression of cognitive impairment, at least among dogs that already have signs of mild impairment. Estrogens would be expected to have a similar protective role in sexually intact female dogs; unfortunately, too few sexually intact female dogs were available for inclusion in the study to test this hypothesis. There may be a need to evaluate possible methods for counteracting the effects of loss of sex hormones in gonadectomized dogs.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10844211&query_hl=4&itool=pubmed_docsum
Two studies suggest that risk of prostatic adenocarcinoma is increased in neutered, compared to intact male dogs.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1492567&query_hl=6&itool=pubmed_docsum
Substitution of castrated rats with a low dose of T [Testosterone], restoring their serum T concentrations to the normal range, completely abolished these perturbations of insulin sensitivity. It is concluded that T is an important regulator of muscular insulin sensitivity, which seems to be highest in a 'window' of normal serum T concentrations.
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http://www.gsdl.com/news/digests/cardiodigest/index10.html
Hormones, especially testosterone, estradiol, IGF-1, and DHEA, influence muscle tone, insulin sensitivity, and lipid metabolism. And it's hardly coincidental that just at the time in a person's life that hormone balance begins to swing toward the lower end of reference ranges, cardiovascular dysfunction also increases.

A host of studies have demonstrated the effect of adequate levels of this hormone on general well being, lean muscle mass, and healthy metabolism, including cardiac function and detoxification. Along with its other benefits in aging men, testosterone plays a role in establishing a foundation for cardiac health.
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http://www.pnas.org/misc/archive062802.shtml
The transgenic mice developed by Vicki Davis from Cedars-Sinai Medical Center and colleagues provide further evidence that estrogen is essential for the inhibition of age-related cataracts and keeping the lens clear.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11195826
Infectious diseases, however, were more common in dogs that underwent prepubertal gonadectomy.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=14765797
Among female dogs, early-age gonadectomy was associated with increased rate of cystitis and decreasing age at gonadectomy was associated with increased rate of urinary incontinence. Among male and female dogs with early-age gonadectomy, hip dysplasia, noise phobias, and sexual behaviors were increased, whereas obesity, separation anxiety, escaping behaviors, inappropriate elimination when frightened, and relinquishment for any reason were decreased.

More on Hip Dysplasia risk:http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9154197&query_hl=18&itool=pubmed_docsum
Onset of mineralization of the proximal femoral epiphyses and of the right proximal tibial epiphysis was significantly later in dysplastic than in radiographically normal puppies.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15284406
Environmental risk factors [for feline diabetes] in domestic or Burmese cats include advancing age, obesity, male gender, neutering, drug treatment, physical inactivity, and indoor confinement.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11787155
Urinary incontinence after spaying occurred in 9.7% of bitches. This incidence is approximately half that of spaying after the first oestrus. Urinary incontinence affected 12.5% of bitches that were of a large body weight (GT 20 kg body weight) and 5.1% of bitches that were of a small body weight (LT 20 kg body weight.\r\n\r\nHowever, compared with late spaying the clinical signs of urinary incontinence were more distinct after early spaying.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11787153
Early-age neutering does not stunt growth in dogs or cats (a once-held belief), but may alter metabolic rates in cats.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10225598
Tumors occurred with similar frequency in males and females, but the relative risk for spayed females was >4 times that for intact females. For HSA, spayed females had >5 times greater relative risk than did intact females. The risk for castrated males was slightly greater than that for intact males, which had 2.4 times the relative risk of intact females. Thus, neutering appeared to increase the risk of cardiac tumor in both sexes. Intact females were least likely to develop a cardiac tumor, whereas spayed females were most likely to develop a tumor.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8961524&query_hl=8&itool=pubmed_docsum
Incompetence of the urethral sphincter mechanism is uncommon in male dogs. This paper reviews 54 cases. As in the bitch, the condition can occur either as a congenital or as an acquired condition, in which neutering may play a part; larger breeds appear to be at greater risk.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8175472&query_hl=10&itool=pubmed_docsum
Neutering was determined to be the most significant gender-associated risk factor for development of hypothyroidism. Neutered male and spayed female dogs had a higher relative risk of developing hypothyroidism than did sexually intact females. Sexually intact females had a lower relative risk.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2326799&query_hl=12&itool=pubmed_docsum
49 of 80 aggressive male dogs and 25 of 47 female dogs are more gentle after neutering. 10 bitches appeared to be aggressive only after being neutered.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11686788&query_hl=14&itool=pubmed_docsum
These results confirmed the gain in body weight and body fat following neutering and demonstrated a strong linear relationship between body fat and serum level of leptin.
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15577502&query_hl=2&itool=pubmed_DocSum
Sterilization of either gender increased the prevalence of anterior cruciate ligament injury, suggesting a potential effect of gonadal gender on prevalence of injury of this ligament.
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http://www.medscape.com/medline/abstract/8722513
Our research nevertheless demonstrates that ovariohysterectomy decreases smooth muscle mass and connective tissue; it also elevates vascular plexus volumes in the urethra of spayed animals. Moreover, our results imply a general weakening of the urethral wall as a sequel to ovariohysterectomy, and this, in turn, could be seen to affect the closure mechanism of the urethra.
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http://jama.ama-assn.org/cgi/content/full/294/20/2601?ijkey=3a6f4b4fe1d61a3b0d7db16bf16acb606e5c671c
Both human studies5-7 and animal models8-9 have demonstrated improved insulin sensitivity and glucose tolerance during lactation compared with nonlactating mothers who served as controls. These differences were independent of weight change.

These findings suggest that maternal lactation may reduce future risk of type 2 diabetes.
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(Ms. X again) Now is all this to say the neutering is all bad and intact is all good? Of course not. Because in the final analysis, there have been many, many, manymanymanymany animals that lived long, full, healthy lives both neutered AND intact.

However you won't find much of this information merely by Googling for "neuter effects". Instead you will find page after page touting the benefits of neutering at any ages - with little mention of risks.

So Ms. X provides this blog to help fulfill her mission of sharing real educational insights, and going to ground after emotional hype.