Puberty.

Telephone conversation between Brock and one of his friends who had a sleepover and stayed up too late:

Brock: Dude! You've got to take care of yourself. You're going through puberty.

I suppose it's a good thing that Brock isn't embarrassed about puberty. He throws the word around all the time. Like to the waitress, "I'll have the cheeseburger and fries. I'm really hungry. I'm going through puberty."