Testosterone propels our drive for exploration and risk, for competition and creation, and even our survival. The effects of testosterone permeate the traditions, philosophy, and literature of every known culture—without it, the world would be a drastically different place.

It also has a role in humanity's darker side, contributing to violence, hubris, poverty, crime, and selfishness. Recent revelations of the science of testosterone show that high levels will deplete compassion and generosity, and even reduce the affection we show our children.

In The Virility Paradox, internationally renowned oncologist and prostate cancer researcher Charles Ryan explores this complex chemical system responsible for a diverse spectrum of human behaviors and health in both men and women. Ryan taps his vast experience treating prostate cancer with testosterone-lowering therapy, observing that this often leads to profound changes in the patients’ perspectives on their lives and relationships. Often, for the better.

He also explores the connections between testosterone and conditions like dementia, autism, and cancer, as well as the biological underpinnings of sexual assault and the effects it has on on everything from crime to investing to everyday choices we make.