Introduction Where many studies on the effects of hormonal treatment (HT) in trans persons focus on objective changes (like body composition or bone density), only few studies evaluated the subjective effects of HT. Therefore, the aim of this study is to evaluate self-reported subjective symptoms during the first year of HT in transgender individuals.

Methods This study is part of the European Network for the Investigation of Gender Incongruence (ENIGI), a multi-center prospective cohort study. For this study, 433 trans persons from the gender clinics of Amsterdam, Ghent and Florence were included. Self-reported symptoms in the areas of psychovegetative symptoms, physical complaints, cognition, emotionality and sexuality, genital complaints and pain were evaluated at baseline and at 3, 6 and 12 months of HT using a 4-point Likert scale (no, mild, moderate or severe complaints). Changes in symptom scores were analysed using mixed models.

Results For trans women in the first 12 months of HT, the largest and persistent effects observed were an increase in breast tenderness, a decrease in sexual desire and an increase in persisting fatigue. For trans men in the first 12 months of HT, the largest, persistent effects observed were an increase in sexual desire, voice instability and acne. For trans men, the largest transient increases were seen for weight gain and clitoral pain.

A part of the symptoms did not show any change during the first 12 months of HT, for example palpitations, dizziness and memory loss.

Conclusion HT causes changes in self-reported symptoms all investigated areas besides cognition. Most symptoms were as expected and even desired while others may be considered disturbing. Most effects are in line with known actions of sex hormones. Knowledge on occurrence of these subjective effects may help doctors informing trans persons starting with and during HT.