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Much research has been conducted on sexual differences of the human brain to determine whether and to what extent a brain gender exists. Consequently, a variety of studies using different neuroimaging techniques attempted to identify the existence of a brain phenotype in people with gender dysphoria (GD). However, to date, brain sexual differences at the metabolite level using magnetic resonance spectroscopy (1H-MRS) have not been explored in transgender people. In this study, 28 cisgender men (CM) and 34 cisgender women (CW) and 29 transgender men with GD (TMGD) underwent 1H-MRS at 3 Tesla MRI to characterize common brain metabolites. Specifically, levels of N–acetyl aspartate (NAA), choline (Cho), creatine (Cr), glutamate and glutamine (Glx), and myo-inositol + glycine (mI + Gly) were assessed in two brain regions, the amygdala-anterior hippocampus and the lateral parietal cortex. The results indicated a sex-assigned at birth pattern for Cho/Cr in the amygdala of TMGD. In the parietal cortex, a sex-assigned at birth and an intermediate pattern were found. Though assessed post-hoc, exploration of the age of onset of GD in TMGD demonstrated within-group differences in absolute NAA and relative Cho/Cr levels, suggestive for a possible developmental trend. While brain metabolite levels in TMGD resembled those of CW, some interesting findings, such as modulation of metabolite concentrations by age of onset of GD, warrant future inquiry.

STUDY QUESTION Does gender-affirming treatment prevent full spermatogenesis in transgender women (TW)? SUMMARY ANSWER Adequate hormonal therapy (HT) leads to complete suppression of spermatogenesis in most TW, if serum testosterone levels within female reference ranges are obtained. WHAT IS KNOWN ALREADY Gender-affirming treatment in transgender individuals may involve gender-affirming HT. The effects on spermatogenesis in TW remain unclear. In order to add information from a referral centre for transgender care, we wish to compare results of earlier studies with our population of TW who received a standard hormone treatment. STUDY DESIGN, SIZE, DURATION This was a prospective cohort study part of the European Network for the Investigation of Gender Incongruence (ENIGI), conducted between 15 February 2010 and 30 September 2015. There were 162 TW were included in the ENIGI study at the Ghent University Hospital in Belgium. Participants are included in ENIGI when they first start HT, and follow-up visits occur over the next 3 years. PARTICIPANTS/MATERIALS, SETTING METHODS The study included 97 TW who initiated HT with cyproterone acetate (CPA) plus oestrogens and proceeded with gonadectomy at the Ghent University Hospital. Testicular tissue retrieved during gonadectomy was processed and stained for four different germ cell markers by the Biology of the Testis lab at the Vrije Universiteit Brussel. Subsequent immunohistochemical staining was performed for melanoma-associated antigen A4 (MAGE-A4, marker for spermatogonia and early spermatocytes), boule homologue, RNA-binding protein (BOLL, marker for secondary spermatocytes and round spermatids), cAMP-responsive element modulator (CREM, marker for round spermatids) and acrosin (marker for acrosome visualization). Serum levels of sex steroids were measured prior to surgery. MAIN RESULTS AND THE ROLE OF CHANCE Suppressed testosterone levels ( LIMITATIONS, REASONS FOR CAUTION Testicular function of the participants prior to initiation of HT was not assessed, although all participants presented with cisgender male serum testosterone values before initiation of HT. The current study only reports on people using CPA at a fixed dose and may therefore not be applicable to all TW. WIDER IMPLICATIONS OF THE FINDINGS HT leads to complete suppression of spermatogenesis in most TW, if serum testosterone levels within female reference ranges are obtained. Serum testosterone levels are associated with the sperm maturation rate. It is important to discuss sperm preservation before the start of hormone therapy. If serum testosterone levels remain higher, spermatogenesis may still occur. STUDY FUNDING/COMPETING INTEREST(S) D.V.S. is a post-doctoral fellow of the Fonds Wetenschappelijk Onderzoek (FWO; 12M2819N). Processing of the testis specimens was funded by the Biology of The Testes (BITE) research group (Department of Reproduction, Genetics and Regenerative medicine at Vrije Universiteit Brussel (VUB)). There are no competing interests. TRIAL REGISTRATION NUMBER N/A.

Introduction: Aromatization of exogenous testosterone might result in increased estradiol levels. Concerns have been raised about undesired estrogenic effects in assigned female at birth (AFAB) transgender people. How serum estradiol levels change after initiation of testosterone therapy and if these levels should be monitored, remains unclear. Methods: This prospective cohort study was part of the European Network for the Investigation of Gender Incongruence (ENIGI). Serum levels of sex steroids were assessed in 746 AFAB transgender people during a three-year follow-up period, starting at the initiation of hormone treatment. Results: Estradiol levels decreased from median [P25-P75] 45.5[24.0-102.2]pg/mL to 36.5[25.0-46.2]pg/mL over three years (P

Background: Previous studies have cross-sectionally described amenorrhea in cohorts of transgender men on intramuscular or subcutaneous testosterone injections. It remains uncertain which testosterone preparations most effectively suppress vaginal bleeding and when amenorrhea occurs after testosterone initiation.Aim: To investigate the clinical effects of various testosterone preparations on vaginal bleeding and spotting in transgender men.Methods: This prospective cohort study was part of the European Network for the Investigation of Gender Incongruence (ENIGI). Data on the persistence and intensity of vaginal bleeding and spotting, serum sex steroid levels and body composition were prospectively and cross-sectionally assessed in 267 transgender men during a three-year follow-up period, starting at the initiation of various testosterone preparations.Results: After three months of testosterone, 17.9% of transgender men reported persistent vaginal bleeding and 26.8% reported spotting. The percentages reporting vaginal bleeding and spotting decreased over the first year of testosterone (bleeding 4.7% and spotting 6.9% at 12 months, respectively), with no participants reporting vaginal bleeding or spotting after 18 months of testosterone. Factors associated with vaginal bleeding or spotting included lower serum testosterone levels and being on testosterone gel as compared to injections (e.g., esters or undecanoate preparations). If vaginal bleeding persisted, starting progestogens at three months resulted in a decrease in the intensity of vaginal bleeding and spotting.Discussion: Transgender men and hormone-prescribing providers can be reassured that vaginal bleeding and spotting usually stop within three months after testosterone initiation. If not, serum testosterone levels should be measured and testosterone dose adjusted to achieve serum testosterone levels in the physiologic male range. Adding a progestin can be considered after three to six months if bleeding persists. Providers should be aware that cessation of bleeding can be more difficult to achieve in transgender men with lower serum testosterone levels or those on testosterone gel.

Purpose: Concerns have been raised about undesired estrogenic effects in assigned female at birth (AFAB) transgender people on testosterone therapy. How serum estradiol levels change after initiation of testosterone therapy and if these levels should be monitored remain unclear. Methods: This prospective cohort study was part of the European Network for the Investigation of Gender Incongruence. Serum levels of sex steroids were assessed in 746 AFAB transgender people during a 3-year follow-up period, starting at the initiation of hormone treatment. Results: Estradiol levels decreased from median [P25-P75] 45.6 [24.0-102.2] pg/mL to 36.5 [25.0-46.2] pg/mL over 3 years (p < 0.001); a change was already noticeable during the first 3 months (mean -17.1 pg/mL, 95% confidence interval -23.8 to -10.6, p < 0.001). Serum estradiol levels were lower in people without endogenous estradiol production from ovarian source (contraceptive users or post hystero-oophorectomy) at baseline and after 3 months, compared with people with endogenous estradiol production. Using long-acting testosterone undecanoate injections resulted in a more prominent decrease in serum estradiol values over 12 months, compared with short-acting mixed testosterone esters (p < 0.001) or testosterone gel (p = 0.001). Changes in serum estradiol were positively correlated to changes in luteinizing hormone (ρ = 0.107, p < 0.001) and negatively correlated to changes in follicle-stimulating hormone levels (ρ = -0.167, p < 0.001) and body mass index (ρ = -0.082, p < 0.001). Conclusion: Testosterone administration in AFAB transgender people resulted in decreasing serum estradiol levels. Our results suggest that testosterone therapy leads to central suppression of estradiol production, with partial restitution due to aromatization.