Growing up is hard on its own, without Hormone Monsters, and the show is well aware of that, as the incredible creatures are actually quite helpful in explaining what a young mind and body are going through at that time. The males are aroused by the most random things, while the girls learn how to cope with their sexuality.
The show tackles various issues, like exploring one's sexual preferences, first period or first kiss, and presents them just as they are to those experiencing them - often unpleasant and strange. The situations that happen to the characters seem very real. For example, Jessi gets her first period during a school trip, as she's wearing white shorts, while Andrew ejaculates publicly during a school dance.
The Hormone Monsters give a more humorous twist to the transformations experienced by the characters, but in the end, everything that happens is very believable. And awkward.