In this remote village, some boys don’t grow a penis until they’re 12

In this remote village, some boys don’t grow a penis until they’re 12
As covered by Michael Mosley in the new BBC series, Countdown to Life: The Extraordinary Making of You, the remarkable case of the Guevedoces is a condition that affects just over 1% of the boys born in Salinas, a remote village lying in the southwest of the Dominican Republic.

Guevedoces (literal translation “penis at 12”) appear to be completely female at birth and are brought up to be little girls.
“When they’re born, they look like girls with no testes and what appears to be a vagina,” writes Mosley for The Telegraph. “It is only when they near puberty that the penis grows and testicles descend.”

At conception we all inherit a set of genes from our parents that will, in time instruct our bodies to make us male or female. But for the first few weeks of our lives human embryos are neither. Instead we have a protrusion called a tubercle. If you’re genetically male the Y chromosome instructs the gonads to become testicles. They also send testosterone to the tubercle, where it is converted into a potent hormone called dihydro testosterone This transforms the tubercle into a penis. If you’re female and don’t make dihydro testosterone then your tubercle becomes a clitoris.
 
When Dr Imperato investigated the Guavadoces she discovered the reason they don’t have male genitalia at birth is because they are deficient in an enzyme called 5 -α -reductase, which normally converts testosterone into dihydro-testosterone. So they appear female when they are born, but around puberty, when they get another surge of testosterone, they sprout muscles, testes and a penis.

Article:
http://www.telegraph.co.uk/news/science/science-news/11874983/Dr-Michael-Mosely-growing-a-penis-at-12.html

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