Questions involving gender development, gender diversity, and differences of sex development sit at the intersection of biology, clinical practice, mental health, ethics, and lived experience. Patients and families may encounter complex decisions across childhood, adolescence, adulthood, reproductive care, and participation in public life. Constructive medical discussion therefore requires careful attention to evidence, uncertainty, autonomy, wellbeing, and the diversity of individual circumstances.

This theme issue brings together Medical Research Archives articles examining that landscape from complementary perspectives. The collection considers biological influences on gender development, the aetiology of differences of sex development, intersex fertility and medical ethics, competing approaches to care for gender-diverse youth, lived experience across the life course, the physical and psychological wellbeing of DSD and transgender athletes, and inclusive mental-health services. Together, the papers provide a multidisciplinary basis for informed, patient-centered dialogue in an evolving area of medicine and public health.