Hormone Monsters are monsters that aid human beings as they go through puberty. Although they are mainly for teenagers going through regular puberty, there are other hormone monsters that assist adults people with adult versions of "puberty", such as menopause and impotence.
- Maury - The first Hormone monster that is introduced overall. He loves promoting his clients to indulge in self-pleasure and explore their sexualities, but as his sexual desires commonly cause him to prompt his clients to make rash (and often dreadful) decisions. His clients include Andrew Glouberman, Matthew MacDell and Duke Ellington. He also owns a collection of furry penises which occasionally appear in episodes. Maury is amoral, sex-crazed, funny and loud.
- Connie - The first hormone monstress and second to be introduced overall. She is witty, energetic, and loyal. She often gets emotionally invested with her clients, experiencing their ups and downs right by their side. Connie is well-meaning but often impulsive, causing her clients to act out when they feel upset. She has a bit of a "friends with benefits" situation with Maury and her clients include Jessi Glaser and Nick Birch, but she resigned as Nick’s hormone monster. It could also be assumed she is Gina's hormone monstress when she appeared at the start of Dark Side of the Boob and she is Missy's former monstress when she appeared in The Head Push. Her full name, is Constance.
- Rick - The second male hormone monster. He is extremely old, disgusting, repulsive as well as rather messed up in the head. He walks with a cane and has a nearly incomprehensible voice that requires subtitles. Rick was Coach Steve's hormone monster and he was obviously very bad at the job as Steve has very minimal knowledge of intercourse or puberty. He was also briefly Nick Birch’s hormone monster before he retired, but then was brought out of retirement to be Nick’s hormone monster again.
- Tyler - A very young and ignorant hormone monster. He is new to the job, shown by his lack of knowledge and experience in the field. He was essentially going through puberty himself when he was set with the task of guiding Nick Birch after Rick retired. Tyler is short, small and child-like with chubby cheeks and a boyish personality. He is later fired from being Nick's hormone monster as he was caught working with the Shame Wizard.
- Mona - A second hormone monstress. She was introduced in the episode Disclosure the Movie: The Musical! as Missy's hormone monstress. Mona pushes her clients to get in touch with their sexuality and express their emotions. We get the vibe that she is a bit of a badass and that she could potentially be up to no good. Mona is mischievous, cunning, confident and sexy. She is also said to be more of a fan of Westworld in preference of Game Of Thrones after making an obvious reference to the latter.
- Gavin - A male hormone monster for puberty. He is a very confident man who is at the top of his game. Maurice envies his success and Nick desires his assistance. He is arrogant, brash, strong and a brute. He is shown to have formerly been Natalie's hormone monster before she went on hormone blockers. He appears very briefly in Season 4. Tyler is his assistant who he abuses.
- Stan - A hormone monster of adult male puberty. He went to Las Vegas once and doesn't like dealing with The Shame Wizard's shit.
- Bob - A hormone monster for male puberty. He is a sad, self-deprecating guy, who's terrible at his job and is well-aware of it.
- Lorraine - A hormone monstress. She is a ditzy, flirtatious woman, who Maurice often hits on.
- Celeste - An extremely old and disgusting hormone monstress for adult female puberty, who is essentially a female variant of Rick. She is seen in The Hugest Period Ever unlike the other One-Time hormone monsters.
- A common rule is that hormone monsters are completely invisible to anyone, who hasn't been assigned to that specific monster. However, a small handful of characters have very clearly seen and interacted with hormone monsters that aren't theirs. Such characters include Caleb, Lars, and Jew Fishman.
- In "Smooch or Share", it is revealed that all of the hormone monsters swear a "jizzocratic" oath.