Abstract
Gender dysphoria (GD) is defined as a condition wherein a person's gender identity does not align with the sex assigned at birth. Oxytocin (OXT) is an essential neuromodulator involved in cognition and socio-emotional processing. Its central effects are exerted via oxytocin receptors (OXTR). Recent studies indicated that the changes in the levels of OXTR may influence the course of some mental disorders (obsessive-compulsive disorders, schizophrenia, depression and autism). Understanding the neurobiological underpinnings of GD, particularly the involvement of OXT and OXTR, could provide beneficial insights into the mechanisms underlying this condition. In the present study, 18 Female-to-Male (FtM) transgenders, 11 FtM transgenders with self-injection of testosterone (FtM-T), and 30 control cis-females were included. Plasma levels of hormones of OXT, estradiol, progesterone, LH, FSH, free testosterone, and testosterone were evaluated with an enzyme-linked immunosorbent assay (ELISA) kit. The whole blood mRNA expression of OXTR was determined via RT-qPCR. Our results showed a statistically significant increase in OXT plasma level in FtM group compared to control group (P = 0.032). Also, OXTR gene expression was significantly high in FtM-T group compared to cis-females group (P = 0.004). This is the first demonstration of increased plasma OXT levels in FtM transgenders and OXTR gene expression in FtM-T transgenders compared to the cis-females group. The results of this study can create a new approach to understanding the underlying mechanism of gender dysphoria. Further studies are necessary to ascertain whether this contributes to or is a consequence of GD symptomatology.