SOME BOYS DON'T GROW PENISES UNTIL PUBERTY

     Can you imagine being raised a girl until you hit puberty and then all of a sudden your balls and penis drop and suddenly, you're a boy? That's what happened to me! Just kidding! But apparently it's an epidemic in the Dominican Republic! (Sorry, Eddie!) 

     A new BBC series, Countdown to Life: The Extraordinary Making of You, focuses on how prenatal development shapes our lives, has brought new attention to a group of seemingly sex-swapping people in the Dominican Republic. In an article for the BBC Magazine, Michael Mosely talks to families with children that were brought up as girls because they lacked obvious testes or a penis at birth. The local name for these children is "guevedoces," which translates to "penis at twelve." But the change they go through isn't magical. It's an example of how multi-layered and complex human sexual development really is. 

     Basically, this is what happens: The condition is the result of an enzyme deficiency. Guevedoces are genetically male, and have Y chromosomes in all of their cells. Their earliest sexual development is also normal: a gene on the Y chromosome turns the undeveloped gonads of the 7 week old embryo into testes, which soon start pumping out male hormones. Two of those hormones, testosterone and Mullerian-inhibiting substance, are critical for the development of the internal male reproductive system. Testosterone triggers the development of the male reproductive tubing: the epididymis and vas deferens. Mullerian-inhibiting substance breaks down tissues that would otherwise develop into female structures like Fallopian tubes and the uterus. The result is a set of tubes that will carry semen from the testes to the point where the urethra emerges from the bladder. 

      At week 10 of prenatal development, a guevedoces looks like any other male fetus. But his enzyme deficiency is about to make things confusing for his parents. Normally, an enzyme called 5-alpha-reductase-2 would convert testosterone into a hormone called dihydrotestosterone or DHT. Where internal reproductive tissues were sensitive to testosterone alone, the tissues that form the external genitalia are instead sensitive to DHT. When guevedoces are born, their external genitalia look female even though their internal reproductive structures are male. They are raised as girls, but at puberty, the testes inside their abdomens start producing large amounts of testosterone. The effect is actually quite startling.

     During puberty, testosterone makes the penis and testes grow into their larger adult form. The same thing happens to the guevedoces, but since their penis starts closer to the size of a clitoris, there's a lot more growing to do. They also develop other male characteristics such as facial hair, a deeper voice, and male masculature. And in most cases, they adapt to their new male bodies. Just look at Big Papi. Again, I'm kidding!

     I'm just blown away by this phenomenon and am totally watching this special on the BBC. It's absolutely crazy, but as I looked at old family photos I noticed my mom used to dress me like a girl until puberty. Should I be worried? Do any of you actually think this is even possible? I mean it's almost like a dog. Their balls don't drop until they're about 7 or 8 months old. I'm still waiting for my penis to grow. Just saying...