British pediatrician Hilary Cass has been investigating the state of gender medicine through the UK's Gender Identity Development Service, and her interim report
"highlights major gaps in research on outcomes of treatment for gender dysphoria and a lack of routine and consistent data collection, making it difficult to design an evidence based assessment and treatment model. The small studies that have been done were mainly on birth registered boys displaying gender incongruence from an early age, who used to be the main cohort seeking treatment."