Hormones are not just the chemicals that make teenagers moody and impossible during puberty, they control metabolism, sleep and our immune systems.
Dr Randi Epstein says understanding human hormones and the important work they do can unlock mysteries about the human body.
Her book is called Aroused: The History of Hormones and How They Control Just About Everything.
She tells Afternoons' Jesse Mulligan hormones were discovered in 1848 by a German doctor doing a fairly bizarre experiment in his backyard.
"The really weird thing he did was put the testicles of one rooster inside the belly of a castrated rooster.
"[He was investigating] could this potentially secreting thing work wherever it was placed in the body? And it did."
She said it was put in a journal and lived on shelves until it was discovered by scientists in England, who did further experiments.
She says hormones seem to affect all sorts of things in our bodies, and it's far more complex than was thought in the past.
"Hormones can make us moody but they don't make us stupid. They're not just 'women going off the rails' they're all of us.
"I like to say that hormones are like your internal wifi, your wireless internet, because they just know, they just kind of go through your body's cyberspace and know exactly where the target to get at [is].
"They never really work alone and that's what we're really finding out now.
"They work in pairs in a whole network of other hormones, they work in conjunction with our immune system, and that's what really keeps the body in check.
"There's so many hormones and there's even more than we ever thought: there's brain signals, there's hormone helpers.
"We're discovering these new ones every day with these long, multisyllabic names.
"That's why if you take too much of one hormone it's not going to mean 'okay you're just going to grow more,' it's going to fiddle with all of the other hormones in your body and may even wreak havoc on your immune system.
That's not good news for those hoping for a quick fix for their growing waistline.
"Here's what we know: Do hormones control hunger and appetite? Absolutely. Is it one hormone or two and we can just tweak this one or that? Unfortunately, we're complicated creatures.
"Among people that have a defect in Leptin … they are voraciously hungry all the time, and they are compelled to eat. For those people, for some of them, they can get leptin shots and they're basically cured of this horrible, uncomfortable hunger all the time.
Like most cures though, it's not for everyone.
"I met one young child who, his defect isn't because he doesn't have enough leptin, his defect is about the way leptin works in his body.
"For most of us, there's no cure for keeping us as hungry as we should be or as full as we should be.
She says the link with the immune system and the potential for curbing the side effects of cancer treatments are the next big frontier in hormone research.