Doctors who see kids with gender-identity issues often attribute their increasing numbers to media coverage. Many of the stories on television are enthusiastic: the kids are adorable; the parents are so convinced. The story with the biggest reach has been that of Jazz, who was born a boy and socially transitioned while still a toddler. At six, he appeared on “20/20” as a mermaid-loving, lip-gloss-wearing girl. Jazz was subsequently interviewed on “60 Minutes” and starred in a documentary, “I Am Jazz: A Family in Transition,” that aired on the Oprah Winfrey Network. Jazz’s parents have started an advocacy organization, the TransKids Purple Rainbow Foundation. A YouTube clip in which Jazz explains that she has “a girl brain and a boy body” has been viewed more than a million times. Now, at twelve, Jazz has started a regimen of puberty-blocking hormones.