BBC Magazine on the extraordinary lives of the Guevedoces, children who suddenly develop male sexual characteristics at puberty:
The discovery of a small community in the Dominican Republic, where some males are born looking like girls and only grow penises at puberty, has led to the development of a blockbuster drug that has helped millions of people, writes Michael Mosley.
Johnny lives in a small town in the Dominican Republic where he, and others like him, are known as “Guevedoces“, which effectively translates as “penis at twelve”.
We came across Johnny when we were filming for a new BBC Two series Countdown to Life, which looks at how we develop in the womb and how those changes, normal and abnormal, impact us later in life.
Like the other Guevedoces, Johnny was brought up as a girl because he had no visible testes or penis and what appeared to be a vagina. It is only when he approached puberty that his penis grew and testicles descended.
[…]
So why does it happen? Well, one of the first people to study this unusual condition was Dr Julianne Imperato-McGinley, from Cornell Medical College in New York. In the 1970s she made her way to this remote part of the Dominican Republic, drawn by extraordinary reports of girls turning into boys.
When she got there she found the rumours were true. She did lots of studies on the Guevedoces (including what must have been rather painful biopsies of their testicles) before finally unravelling the mystery of what was going on.
When you are conceived you normally have a pair of X chromosomes if you are to become a girl and a set of XY chromosomes if you are destined to be male.
For the first weeks of life in womb you are neither, though in both sexes nipples start to grow.
Then, around eight weeks after conception, the sex hormones kick in. If you’re genetically male the Y chromosome instructs your gonads to become testicles and sends testosterone to a structure called the tubercle, where it is converted into a more potent hormone called dihydro-testosterone This in turn transforms the tubercle into a penis. If you’re female and you don’t make dihydro-testosterone then your tubercle becomes a clitoris.
