The research in this article is neutral in nature. We gathered the information from various medical studies and put it all together in this article. It is going to give you the pros and cons of health issues in desexed dogs as well as intact dogs. The consensus is that whether you decide to desex your dog or not, something positive or negative is going to come out of it. This research will help you to navigate your choice on whether to have the procedure done or not. If you do decide to have your dog desexed, the best time to do it is when they have finished growing.
For small and medium dogs (5 lbs-50 lbs), a safe age to have the procedure done is around 10 months of age. For large and giant dogs (50 lbs+), a safe age to have the procedure done is around one year of age. Just remember that this is just a range to help you. It is going to be dog dependent, breed dependent, and choice dependent. Always consult your veterinarian before making a decision. If you already have a dog that has been desexed at an early age, or you feel as they may have a hormonal imbalance, there are hormone products out there that will help to balance your dog out.
- The dogs were classified as intact (not neutered), neutered before 6 months, neutered between 6 to 11 months, or neutered between 12 to 23 months and 2 to 8 years.
- A report in 2004 evaluated dogs with early neutering. Such findings resulted in a greater scrutiny of the potential adverse effects of neutering on health conditions, especially since it is well-known that different physiological systems and behavioral responses rely upon gonadal steroids during development.
- Dogs are altricial and therefore more reliant on postnatal hormones for musculoskeletal development.
- It is quite likely that any orthopedic risk associated with neutering reflects the age of neutering. Linear bone growth represents an interplay of gonadal hormones, pituitary hormones, and growth factors with gonadal steroids playing a prominent role in growth plate closure. The removal of the sex hormones prior to initiation of growth plate closure would promote the continued proliferation of cells within the growth plate thus permitting bone elongation that exceeds the normal growth period. Growth cessation differs for different bones within the body and the closure and growth is tightly orchestrated to optimize joint configuration. Neutering prior to cessation of bone growth would impact bone elongation and joint formation. Large breed dogs have a longer growth period than smaller stature dogs and thus bone/joint articulation may be more susceptible to environmental and exogenous perturbations in the large breeds.
- Female dogs, as also seen in humans and mice, are more prone to immune-mediated disorders and neutering appears to exacerbate that risk. The risk of certain immune diseases is elevated with neutering in both males and females: atopic dermatitis, autoimmune hemolytic anemia, hypoadrenocorticism, hypothyroidism, immune-mediated thrombocytopenia, inflammatory bowel disease, and systemic lupus erythematosus. For dogs diagnosed with hypoadrenocorticism, the relative risk of death is 2-fold higher than that seen for other dogs.
- A sex effect on risk for immune disorders related to neutering is consistent with the risk noted for cancers as impaired immune function is also associated with cancer progression. Gonadal steroids exhibit differential effects on the immune system and are believed to account for the sex specific susceptibility to immune and autoimmune disorders. Estrogens, acting through their cognate receptors, are critical modulators of both innate, and adaptive immune function. Estrogens increase the production of immunoglobulins, thereby enhancing the humoral immune response as exemplified by females exhibiting a greater antibody response to vaccines. Estrogens can enhance the production of autoantibodies and preferentially stimulate IgM production, the immunoglobulin form most predominant in autoimmune disease. Thus, immunoglobulin production induced by estrogen has been implicated in mediating autoimmune pathologies especially as estrogens impair the body's process of removing autoreactive B cells.
- When aggregated data for all dogs across multiple breeds are analyzed, neutering increases the overall risk of hemangiosarcoma, lymphoma, mast cell tumors, and osteosarcoma in both sexes although females exhibit a greater risk when neutered than seen for neutered males across all these cancers. Another broadly based retrospective study reported an increased risk associated for lymphoma and mast cell tumors across both sexes and only increased risk for hemangiosarcoma in females and osteosarcoma in males associated with neutering.
- For many cancers exhibiting a genetic predisposition, being neutered increases risk. In contrast, the incidence of cancers associated with the reproductive tract are reduced. For instance, the risk of mammary tumors, known to have a genetic component is greatly reduced with neutering. Neutering also reduces the risk of testicular cancer and perianal adenomas.
- In an all-breed analysis, neutered males had elevated risk for intervertebral disk disease (IVDD).
- 7% percent of intact males were diagnosed with one or more joint disorders, compared to 21% of males neutered prior to 1 year of age.
- 5% of intact females were diagnosed with one or more joint disorders, compared to 16% of females neutered prior to 1 year of age.
- Mammary neoplasia (cancer of the mammary glands) is 7 times more likely in un-spayed female dogs than in those that have been spayed; the incidence of this cancer ranges from 3.4% to 13%. Optimal spay age to avoid mammary neoplasia in female dogs is less than 2.5 years.
- Urinary incontinence, not diagnosed in intact females, was diagnosed in 7% of females neutered before 1 year of age.
- Benign prostatic hypertrophy/hyperplasia (a non-cancerous, enlarged prostate) occurs in more than 50% of intact male dogs, with incidence increasing with age.
- 4 out of 5 studies show an increase in prostate cancer in neutered dogs; however, this cancer arises in only 0.2% to 0.6% of the population.
- Testicular neoplasia, with an incidence of 0.9%, is only seen in intact male dogs.
- Pyometra (inflamed or infected uterus) occurs in roughly 25% of intact female dogs.
- Of males castrated early—defined in this study as before 1 year of age—10% had hip dysplasia, double the occurrence among sexually intact males. Cranial cruciate ligament tears were not diagnosed in any of the sexually intact males or females, but in the early age–neutered males and females, prevalences were 5% and 8%. Lymphosarcoma was diagnosed in almost 10% of males castrated early, 3 times the rate in sexually intact males.
- Researchers found the percentage of females spayed at 1 year of age or later that developed hemangiosarcoma (about 7%) was more than 4 times the percentages of sexually intact and early age–neutered females that developed hemangiosarcoma. None of the sexually intact females developed mast cell tumors, but nearly 6% of females spayed at 1 year of age or later did.
- Researchers have reported higher incidences of musculoskeletal and endocrinologic disorders, obesity, and urinary incontinence in neutered mixed-breed and pedigreed cats and dogs, compared with incidences in sexually intact animals.
- Labrador Retriever (1,500 cases: males–272 neutered, 536 intact; females–347 neutered, 345 intact)
The findings on the Labrador Retriever are published. The major finding was a significant 2- fold increase in one or more joint disorders with neutering in the first year in both males and females above the 5 percent level of intact dogs. The occurrence of the cancers followed was low (3-4%) and not affected by neutering.
- German Shepherd (1,170 cases)
The paper is under review. Early neutering significantly increased the incidence of one or more joint disorders and the occurrence of the cancers followed was low and not affected by neutering.
- Small-dog Breeds
Chihuahua (831 cases)
Yorkshire Terrier (553 cases)
Shih Tzu (322 cases)
These breeds lacked joint disorders associated with neutering at any age above the low incidence of intact dogs. The occurrence of one or more cancers was low in both intact and neutered dogs.
- Long-dog breeds Dachshund (548 cases) Corgis (191 cases)
Joint disorders in these breeds were not associated with neutering at any age above the low incidence of intact dogs. The occurrence of one or more cancers was low in both intact and neutered dogs. In male and female Dachshunds the occurrence of intervertebral disc disorders was high in intact dogs and not increased by neutering.
- Rottweiler (696 cases)
Males and females showed an increase above intacts in one or more joint disorders with early neutering. The incidence of one or more of the cancers was not increased in either gender by neutering at any age.
- Boxer (645 cases)
There was no increase in joint disorders associated with neutering at any age above the low incidence in intact dogs. Intact males had a fairly high incidence of cancers, which was increased in one of the neuter periods. Intact females had a fairly high incidence of cancers, not increased by neutering.
- Doberman Pinscher (295 cases)
In males, there was no increase in one or more joint disorders associated with neutering above the low level in intact males. In females, however, there was an elevated incidence of joint disorders in an early neuter period, compared to none in intact females. In both sexes, the occurrence of cancers was less than the low level in intact dogs and not markedly affected by neutering.
- Bulldog (471 cases)
The moderate occurrence of one or more joint disorders in intacts appeared not to be increased with neutering in males and females. For cancers, there was no evident increase in occurrence associated with neutering above the moderate level of intact male and female dogs.