I know an 11 year old boy with this. He is a lovely chap, full of energy and enthusiasm, however he needs to take medication at exactly the same time each day. Obviously he has to be careful, but unless you know his background story you wouldn't know he had any problems.
My 30 year old wife found out today that she has no pituitary gland. The beauty of the human body is the brain will compensate for the lack of the gland. Other parts of the brain will take over the function(s) of the pituitary. She does, however, have issues that she has dealt with all her life and so will any child with the same condition.
I have been trying to look up information on this subject myself. I have a grandson that just turned three and going strong that was born without a pituitary gland.
My boyfriend was born without a pituitary gland. As a child he used to have to take testosterone shots and was smaller than most of the other children, but now at twenty one he's fine and takes no medication for this.