Metabolism, behavior, sleep, mood swings, the immune system, fighting, fleeing, puberty, and sex: these are just a few of the things our bodies control with hormones. Armed with a healthy dose of curiosity, medical journalist Randi Hutter Epstein, adjunct assistant professor of journalism, takes us on a journey through the unusual history of these potent chemicals from a basement filled with jarred 19th-century brains to a 21st-century hormone clinic in Los Angeles. Brimming with anecdotes, new medical research, and humorous details, Epstein explores the functions of hormones such as leptin, oxytocin, estrogen, and testosterone, demystifying the science of endocrinology and introducing the leading scientists who made life-changing discoveries about hormones—and the charlatans who used those discoveries to peddle false remedies.