Personally, depending upon breed I wouldn't neuter until your dog is mature, irrespective of health issues, there are numerous behavioural issues that neutering can bring about. There is a second fear period that all dogs go through, and removing testosterone CAN in some dogs cause them to develop nervousness &/or fearful aggression, not to mention other behaviours. It is best to wait until a dog of either sex is mature for their breed, for most dogs that won't be until 2 years of age at the earliest.