Positive for male neutering
- eliminates the small risk (probably < 1%) of dying from testicular cancer
- reduces the risk of non-cancerous prostate disorders
- reduces the risk of perianal fistulas
- may possibly reduce the risk of diabetes (data inconclusive)
- if done before 1 year of age, significantly increases the risk of osteosarcoma (bone cancer); this is a common cancer in medium/large breeds with poor prognosis
- increases the risk of cardiac hemangiosarcoma by a factor or 1.6
- triples the risk of hypothyroidism
- increases the risk of progressive geriatric cognitive impairment
- triples the risk of obesity, a common health problem in dogs with many associated health problems
- quadruples the small risk of (<0.6%) of prostate cancer
- doubles the small risk (<1%) of urinary tract cancer
- increases the risk of orthopedic disorders
- increases the risk of adverse reactions to vaccination
- if done before 2.5 years of age, greatly reduces the risk of mammary tumors, the most common malignant tumors in female dogs
- nearly eliminates the risk of pyometra, which otherwise would affect about 23% of intact female dogs; pyometra kills about 1% of intact female dogs
- reduces the risk of perianal fistulas
- removes the very small risk (< 0.5%) from uterine, cervical and ovarian tumors
- if done before 1 year of age, significantly increases the risk of osteosarcoma (bone cancer); this is a common cancer in the large breeds with a poor prognosis
- increases the risk of splenic hemagiosarcoma by a factor of 2.2 and cardiac heangiosarcoma by a factor of >5; this is a common cancer and major cause of death in some breeds
- triples the risk of hypothyroidism
- increases the risk of obesity by a factor of 1.6-2, a common health problem in dogs with many associated health problems
- causes urinary "spay incontinence" in 4-20% of female dogs
- increases the risk of persistent or recurring urinary tract infections by a factor of 3-4
- increases the risk of recessed vulva, vaginal dermatitis and vaginitis, especially for female dogs spayed before puberty
- doubles the risk(<1%) of urinary tract tumors
- increases the risk of orthopedic disorders
- increases the risk of adverse reactions to vaccination
http://www.naiaonline.org/pdfs/longtermhealtheffectsofspayneuterindogs.pdf