Sex Steroids and the Serotonin Transporter

The aim of this study is to prove the influence of the sex steroid hormones estrogen, progesterone and testosterone on the serotonin transporter (5-HTT) binding using positron emission tomography (PET) and the selective radioligand \[11C\]DASB. Specifically, the 5-HTT binding will be quantified before and after hormone therapy underwent by 10 male-to-female (MtF) and 10 female-to-male (FtM) transsexuals urging for hormone treatment. The high-level, long-term administration of opsite sex steroid hormones in transsexuals provide the unique opportunity to investigate the influence of sex steroid hormones on the serotonergic system. Since the serotonin transporter serves as a primary target molecule for antidepressant treatment, the results of the study will be of benefit for the assessment of the clinical relevance of estrogen and testosterone as modulatory and neuroactive agents.