Hi,
Welcome to health care magic
If you are much worried about
masturbation related side effects thenI would say that masturbation is completely normal when it is done in privacy without hurting genitals.
It is just like 'self sex' and has nothing to do with penis size and also never causes weakness in the body.
Also,Masturbation is a safe way of expressing ones own sexual desires and there is no problem associated with it. It will not cause any problem to the penis physically or sexually.
Size of penis depends on the genetic and racial factors.So, there is no way we can increase the size of penis.
Masturbation never cause shrinkage of penis size as i said it has nothing to do with penis size.
For your information,4 inch size penis is more than enough to satisfy woman during sexual intercourse because initial 2.5 inch vaginal wall or portion is sensitive only and rest of the other vagina is insensitive.
So,it is immaterial that if one has big size of penis then he can more satisfy his sexual partner.
Here,I would advice you to take balanced diet and keep your self healthy and fit otherwise there is no medicine available which increases the size of penis.
Hope it will clear to you now,and if any query then feel free to ask me.
Regards,