Resting state functional connectivity is affected by testosterone treatment in female-to-male transgender persons

Abstract

Background/Aims Several resting state networks have been described in literature. Today, it is still unclear whether these networks are stable or can be influenced by sex hormones. Transgender persons offer a unique opportunity to study these hormonal influences. The present study aimed to examine the effects of cross-sex hormone treatment in transgender persons on two resting state networks involved in cognition and emotion, the default mode network and executive network. Methods Resting state functional magnetic resonance imaging and sex hormone levels were analyzed in 21 female-to-males, 13 male-to-females, 17 untreated control men and 12 untreated control women (all participants were aged ≥ 17). Measurements were done at baseline, when endogenous gonadal stimulation in the transgender participants was suppressed by a gonadotropin-releasing hormone analogue, and four months after the start of cross-sex hormone treatment (testosterone in female-to-males and estradiol in male-to-females). Independent component analysis was used to evaluate the effect of cross-sex hormones. Results Within the default mode network, female-to-males showed increased functional connectivity in the right postcentral gyrus four months after starting testosterone treatment. In the male-tofemales and both control groups no differences in functional connectivity in any of the two networks were observed. Conclusions Functional connectivity within the default mode network appears to be affected by testosterone treatment in female-to-male transgender persons.