This seems like something you start them on later in life. The IGF-1 hormone spurs growth when they are young, but its continued presence after they stop growin

This seems like something you start them on later in life. The IGF-1 hormone spurs growth when they are young, but its continued presence after they stop growing greatly increases their chances of health issues like cancer later in life. So if you start them on it at ~2 years old, they'll still grow to normal size but it will reduce the prevalence of cancers. (at least that seems to be the theory).