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for college after four long years of high school, I had a pretty good idea what Jake and his parents were going through. No matter how harmonious a boy's childhood has been, puberty can change everything. This stage of child development requires that delicate parental maneuver of becoming disengaged without disengaging. Kate said she felt as if the Jake she knew had disappeared, and in some ways he had.
    Scientists have discovered that the teen brain in both sexes is distinctly different from the preadolescent brain . The changes that were becoming obvious in Jake were set in motion by his genes and hormones while he was still in utero. Now, with the end of the juvenile pause, it was time for Jake to ramp up his skills for surviving in a man's world. And he was ready and eager, even if his mother wasn't. At this stage, the millions of little androgen switches , or receptors, in his brain are hungrily awaiting the arrival of testosterone--king of the male hormones. As the floodgates are flung wide open, the juice of manhood saturates his body and his brain. When my own son turned fourteen and became moody and irritable, I remember thinking, "Oh my God, soon the testosterone will take him over mind, body, and soul."

TESTOSTERONE TSUNAMI
    Although Kate worried that Jake's behavior was extreme, I assured her that he was no different from many other boys his age . At fourteen, Jake's brain would have already been under reconstruction for a few years. Between the ages of nine and fifteen, his male brain circuitry, with its billions of neurons and trillions of connections, was "going live" as his testosterone level soared twentyfold . If testosterone were beer, a nine-year-old boy would get the equivalent of about one cup a day. But by age fifteen, it would be equal to two gallons a day. Jake wasn't into drugs or alcohol. He was loaded on testosterone.
    From then on, testosterone would biologically masculinize all the thoughts and behaviors that emerge from his brain . It would stimulate the rapid growth of male brain circuits that were formed before he was born. It also would enlarge his testicles, activate the growth of his muscles and bones, make his beard and pubic hair grow, deepen his voice, and lengthen and thicken his penis . But just as dramatically, it would make his brain's sexual-pursuit circuits, in his hypothalamus, grow more than twice as large as those in girls' brains . The male brain is now structured to push sexual pursuit to the forefront of his mind .
    Early in puberty, when images of breasts and other female body parts naturally take over their brain's visual cortex, some boys wonder if they're turning into "pervs." It takes a little while for them to get used to their new preoccupation with girls, which runs on autopilot . This sexual preoccupation is like a large-screen TV in a sports bar-- always on in the background . When I share this information with teen boys in high-school classrooms, I can see recognition flash across many of their faces, if only for an instant, before they go back to looking bored.
    But sex is not the only thing on a teen boy's mind. As the testosterone surged through Jake's brain cells, it was stimulating Together, Jake's brain territorial about his room and sensitive to his peer's putdowns--perceived or real. And when these hormones got mixed with the stress hormone cortisol, they supercharged his body and brain, preparing him for the male fight-or-flight response in reaction to challenges to his status or turf . Our brains have been shaped for hundreds of thousands of years by living in status-conscious hierarchical groups . And while not all teen boys want to be king of the hill, they do want to be close to the top of the pecking order, staying as far from the bottom as possible . And that can mean taking risks that get them into trouble .
a companion hormone called vasopressin .
testosterone and vasopressin were making
    Like most of us moms, Kate couldn't fully appreciate or