The teen gene: Switching on puberty
By Alison Motluk DID you stare into the mirror every morning, desperate for signs that your body was starting to develop like those of your classmates? Or perhaps you were the one who started sprouting breasts or facial hair years before your peers, and got teased just as much as the late developers. Though it happens to practically everyone, the start of puberty is highly unpredictable: it can happen as naturally to a girl of 8 as to one aged 13. The range is just as wide in boys, though puberty tends to strike them a couple of years later. Though that whole range is considered “normal”, the age at which the hormones start flowing can affect everything from how tall you will grow, how strong your bones will be, your risk of getting breast or prostate cancer many decades later to maybe even your mental health. And it’s entirely out of our hands. Or is it? What triggers puberty has been a long-standing mystery. Why does it come to some so young? Some so old? What gives it the ultimate push, and why does the average age seem to be falling? It’s common knowledge that puberty is a process that starts in the brain, well before the outward signs begin to show. The hypothalamus in the brain suddenly begins secreting gonadotropin-releasing hormone, or GnRH, and this substance unleashes the chemical cascade of puberty (see Diagram). Before we know it, we are reproductive adults, capable of producing mature sperm and eggs and even having our own kids. The question was, what triggers the release of GnRH?