Hi there, I found this information for you..
Deciding whether or not to have your pet neutered can be difficult for many owners. The decision should always be based on individual circumstances. This article aims to give owners some general information so that they are well equipped to make the decision which is right for them.
Both male and female cats tend to become sexually mature and capable of breeding at around six months of age.
If you do not want your cat to breed you should try to reach a decision about how to prevent this by the time your pet reaches this age.
The most reliable method of preventing your cat from breeding is to have him or her surgically neutered. This is known as castration for males and speying for females.
Castration:
Male cats may be neutered under general anaesthetic by a veterinary surgeon. The surgery is normally carried out at around six months of age, but may be performed at any time after this if necessary.
If you decide to keep your male cat entire he will develop the typical characteristics of a "tomcat". His face will develop more pronounced cheeks, his skin will become thicker (although you probably will not notice this) and he will probably grow bigger than a male who is neutered at six months of age. However the disadvantages in keeping an entire male cat include the fact that he is more likely to roam in search of females and therefore may go missing for days or even weeks at a time. He is also more in danger of getting involved in road traffic accidents due to this behaviour. He will probably get involved in fights while protecting his large territory and is more likely to need treatment at the vet's because of this. Male cats often have a distinctive strong odour about them and are more likely to urine spray around the house than neutered cats. Due to fighting and breeding, entire males are at considerable risk of diseases such as FeLV and FIV. Entire male cats can make great pets but many people opt for castration of male cats because they do tend to be easier to keep if neutered.
In the UK we usually neuter at 6 months..
it doesnt seem to make any difference in growth..
certainly many male neuters go on to win at cat shows so it can't do them any harm.