If and when to neuter your dog

This article is aimed at male dogs only.  Female dogs should be spayed before their first heat due to the dramatic reduction in their risk for mammary tumors.  Aside from the fact that mammary tumors are common and up to 50% of them are malignant, I can tell you that I've seen many mammary tumor surgeries and it is heartbreaking to see an animal undergo and recover from surgery to remove an entire chain of mammary glands.  They are cut from their chest to their groin which results in a painful recovery and a lot of management to control swelling.  It's not fun for the animal or the owner.

Males are a little different.  The benefits of neutering a male are:

• eliminates the risk of testicular cancer
• decreased risk of prostate disorders (up to 80% of unneutered males develop some sort of prostatic disease or cancer although it is usually not malignant)
• decreased risk of perianal fistulas (lesions and abscesses that occur around the anus which tend to recur and become chronic, if surgery is necessary there is a risk of fecal incontinence)
• decreased risk of hernias
• fewer behavioral problems (decreased aggression, roaming, and shorter attention span)

The risks of neutering are:

• anesthesia (very low risk for healthy dogs, even lower with proper pre-surgical bloodwork)
• early neutering MAY increase the risk of osteosarcoma (malignant bone cancer) in giant breed dogs
• increased risk of hemangiosarcoma (cancer of the blood vessels, that's an increase of 3% chance to 4.5% chance AT MOST)
• increased risk of osteosarcoma (the earlier the castration the higher the risk; the average lifetime risk of Great Danes is 4%)

To me the benefits and risks, medically, are about even.  But, as a frequent dog park visitor I can tell you that the behavioral benefits of castration are quite great.  The majority of the aggressive dogs I've met at dog parks are intact with most of them being 9 months old.  That seems to be a time when male dogs start feeling that testosterone and testing the waters with the people and dogs around them. 

PS:
I know seeing cancers in the "risks" column is quite scary, but keep in mind that these are small increases of already small risks.  And keep in mind that people tend to write to catch your attention online.  A headline of "Neutering doubles the risk of cancer" would strike fear in the heart of any pet owner, but can be quite misleading if the risk goes from 0.01% to 0.02%.  Sure, the risk doubled, but it's still incredibly low.