Girls become boys upon reaching puberty
For some adolescents living in the village of Salinas in the Dominican Republic, one pubescent change is the development of a penis and testes.
One in 90 boys residing in the area suffer from a rare condition that causes them to be born without male reproductive organs.
Known as Guevedoces — which means 'penis at 12' — these children spend the first decade or so of their lives as girls before turning into boys upon reaching puberty.
According to The Telegraph, Cornell endocrinologist Dr Julianne Imperato found an explanation to the phenomenon after making a trip to Salinas in the 1970s.
Dr Imperato's study found that human embryos only have protrusions called tubercles and remain sexless for the first few weeks of life.
If the embryo is genetically male, the Y chromosome will instruct the gonads, or reproductive glands, to become testicles.
Testosterone is then sent to the tubercle to be converted into a hormone known as dihydro-testosterone, which is responsible for transforming the tubercle into a penis.
In female embryos, dihydro-testosterone is absent and the tubercle transforms into a clitoris instead.
In its TV series Countdown To Life, BBC Two told the story of one of the Guevedoces — a 20-something man named Johnny who was once known as Felicita.
Johnny told BBC Two that he wasn't comfortable spending the initial years of his life as a girl.
He said: "I never liked to dress as a girl and when they bought me toys for girls I never bothered playing with them - when I saw a group of boys I would stop to play ball with them."
When Johnny made the transition from girl to boy, he struggled to fit in with the rest of the children.
He said: "They used to say I was a devil, nasty things, bad words and I had no choice but to fight them because they were crossing the line."
After becoming a man, the next thing on Johnny's mind is settling down with the right woman.
He said: “I’d like to get married and have children, a partner who will stand by me through good and bad.”
Sources: BBC, The Telegraph, Mirror UK