A European Network for the Investigation of Gender Incongruence: Endocrine Part.

INTRODUCTION: Cross-sex hormone therapy is an essential part of gender affirming treatment of transgender individuals. Studies systematically describing the physical and psychological effects of hormonal treatment of transgender persons are scarce.

AIM: The aim of the current protocol is to evaluate clinical and side-effects of cross-sex hormonal treatment in trans persons.

METHODS: The European Network for the Investigation of Gender Incongruence (ENIGI) is a multicenter prospective study. Because of the relatively low prevalence of the condition and small number of specialized centers, international collaboration is warranted. Four European treatment centers, Ghent, Oslo, Florence, and Amsterdam, developed a common study and treatment protocol.

MAIN OUTCOME MEASURES: Outcome measures include hormonal and metabolic parameters, bone density, secondary sex and anthropometric characteristics, and physical and psychological well-being.

RESULTS: Thus far, 333 trans women and 343 trans men have been included in the ENIGI Endocrine protocol. The study is still ongoing.

CONCLUSION: In recent years, the number of trans persons seeking gender affirming treatment has increased. However, well-designed prospective studies evaluating safety and effectiveness of current hormonal treatment protocols are lacking. Therefore we started the ENIGI collaboration. In this article we give a detailed description of the study protocol, objectives, and design of the ENIGI Endocrine protocol.