Dr. Riittakerttu Kaltiala, 58, is a Finnish-born and trained adolescent psychiatrist, the chief psychiatrist in the department of adolescent psychiatry at Finland’s Tampere University Hospital. She treats patients, teaches medical students, and conducts research in her field—publishing more than 230 scientific articles. In 2011, Dr. Kaltiala was assigned a new responsibility. She was to oversee the establishment of a gender identity service for minors, making her among the first physicians in the world to head a clinic devoted to the treatment of gender-distressed young people. Since then, she has personally participated in the assessments of more than 500 such adolescents....