title: A European Network for the Investigation of Gender Incongruence: Endocrine Part.
abstract: 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.
  
  
  
  The aim of the current protocol is to evaluate clinical and side-effects of cross-sex hormonal treatment in trans persons.
  
  
  
  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.
  
  
  
  Outcome measures include hormonal and metabolic parameters, bone density, secondary sex and anthropometric characteristics, and physical and psychological well-being.
  
  
  
  Thus far, 333 trans women and 343 trans men have been included in the ENIGI Endocrine protocol. The study is still ongoing.
  
  
  
  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.
authors.affiliation: Department of Endocrinology, VU University Medical Center, Amsterdam, The Netherlands. Electronic address: m.dekker3@vumc.nl.
authors.forename: M J H J
authors.initials: MJ
authors.lastname: Dekker
authors.affiliation: Department of Endocrinology, Ghent University Hospital, Ghent, Belgium.
authors.forename: K
authors.initials: K
authors.lastname: Wierckx
authors.affiliation: Department of Endocrinology, Ghent University Hospital, Ghent, Belgium.
authors.forename: E
authors.initials: E
authors.lastname: Van Caenegem
authors.affiliation: Department of Endocrinology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Klaver
authors.affiliation: Department of Medical Psychology, VU University Medical Center, Amsterdam, the Netherlands.
authors.forename: B P
authors.initials: BP
authors.lastname: Kreukels
authors.affiliation: Center for Sexology and Gender, Ghent University Hospital, Ghent, Belgium.
authors.forename: E
authors.initials: E
authors.lastname: Elaut
authors.affiliation: Sexual Medicine and Andrology Unit, Department of Experimental, Clinical and Biomedical Sciences, University of Florence, Florence, Italy.
authors.forename: A D
authors.initials: AD
authors.lastname: Fisher
authors.affiliation: Department of Obstetrics and Gynaecology, VU University Medical Center.
authors.forename: M A A
authors.initials: MA
authors.lastname: van Trotsenburg
authors.affiliation: Department of Endocrinology, Oslo University Hospital, Oslo, Norway.
authors.forename: T
authors.initials: T
authors.lastname: Schreiner
authors.affiliation: Department of Endocrinology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: den Heijer
authors.affiliation: Department of Endocrinology, Ghent University Hospital, Ghent, Belgium; Center for Sexology and Gender, Ghent University Hospital, Ghent, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: T'Sjoen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D005783:Gender Identity; D012739:Gonadal Steroid Hormones / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011446:Prospective Studies; D063106:Transgender Persons / Q000523:psychology; D044465:White People; D055815:Young Adult
chemical_list: D012739:Gonadal Steroid Hormones
keywords: Cross-Sex Hormonal Treatment; Gender Dysphoria; Prospective Cohort Study