Effects of Sex Steroid Hormones on Human Brain Function, Structure and Connectivity

Inclusion criteria for transsexuals are: * DSM-IV diagnosis of Gender Identity Disorder (DSM-IV: 302.85, 302.6; ICD-10: F64.9, F64.8) by a structured clinical interview (SCID) * general health based on history, physical examination, ECG, laboratory screening, SCID * willingness and competence to sign the informed consent form Exclusion criteria for transsexuals are: * severe neurological or internal diseases * steroid hormone treatment within 2 months prior to inclusion (including birth control pill, phytohormones) * treatment with psychotropic agents such as SSRIs * any implant or stainless steel graft * abnormal values in routine laboratory screening or general physical examination * current substance abuse (determined using drug screening at the screening visit) * pregnancy (determined at screening visit and first MRI scan) * failure to comply with the study protocol or to follow the instructions of the investigating team. Inclusion criteria for healthy controls are: * general health based on history, physical examination, ECG, laboratory screening, SCID * willingness and competence to sign the informed consent form Exclusion criteria for healthy controls are: * severe diseases * any implant or stainless steel graft * steroid hormone treatment within 2 months prior to inclusion (including birth control pill, phytohormones) * abnormal values in routine laboratory screening or general physical examination * current substance abuse (determined using drug screening at the screening visit) * pregnancy (determined at screening visit and first MRI scan) * failure to comply with the study protocol or to follow the instructions of the investigating team