Hormone control in male dogs...?

Hello- I have a three year old, male ,Australian shepherd. He was neutered as a puppy. My dog has recently started to show signs of aggression, ie. biting my sister. The dog has always been extremely well behaved, though he has always shown signs of dominance. (Humping, marking, ect....that has always been immediately corrected). I have a few thoughts as to why he is so insistent on dominance, the most important being that he is the only male in the house (it just my self, sister and mother). My question is, how do we manage this dog again? In horses, Regu-mate is used in both males (occasionally) and females to control hormones. Is there a similar product that can be given to male dogs in order to suppress hormones and alleviate the dominance?