One June afternoon, JD received a phone call from Mount Sinai Health System, informing him that his teenage daughter’s medical records were being requested by the Justice Department, part of a larger criminal probe into the New York medical institution’s program for transgender youth. JD’s 16-year-old daughter Winter was briefly a patient at Mount Sinai’s youth gender center before switching to a different provider in New York City two years ago. (JD, who is also trans, asked that his family only be identified by their first names to protect their privacy.) But still, her medical records — along with those...