Early in a life, males experience two bursts of testosterone: one tells their genitalia to develop male characteristics, and the other is believed to imprint a male pattern on their brains, writes urologist Abraham Morgentaler, MD, FACS
, in his forthcoming book, Why Men Fake It: The Totally Unexpected Truth About Men and Sex
. From shortly after birth and throughout childhood, though, little boys and girls have the same nearly undetectable levels of testosterone—it isn't until puberty that the hormone surges in guys. But even then, Morgentaler tells us, the average amount of testosterone in a healthy man under the age of 40 is 350 to 1,000 nanograms per deciliter of blood (a Men's Health
writer puts this into perspective: "If you somehow managed to collect all the testosterone from your entire body, it would barely fog the bottom of a shot glass"
). In fact, Morgantaler says that the concentration of testosterone (and many other hormones) is so low that it took about four decades after testosterone's discovery to develop a blood test capable of detecting such tiny amounts.