Evidence suggests that the gonadal steroids may exert clinically significant effects on central nervous system function. For example, the menstrual cycle may influence the occurrence of seizures in some female epileptics and the performance on certain cognitive tests. Central nervous system effects of gonadal steroids have been inferred largely from changes in behavior occurring in association with presumed changes in gonadal steroids during the normal menstrual cycle, during the administration of ovarian hormones, or in a gender-specific context. These inferences are, by definition, indirect and associational in nature and further are incapable of disentangling the effects of hormones which are simultaneously present in women of reproductive age. This study is designed to address those problems by comparing measures during Lupron-induced hypogonadism with those during replacement with estrogen or progesterone. On the basis of prior findings from our group and from others, we will be asking the following questions: 1) Is the decreased r-CBF that we observed in the prefrontal cortex during the hypogonadal state confirmed in individual women using new imaging techniques; 2) Will variation in genotype (e.g., COMT val/met, BDNF val/met) confer differential sensitivity to ovarian steroids in brain circuitry and 3) Are the menstrual cycle phase-related changes in reward systems that we previously observed related to estradiol or progesterone actions within the brain (1). Additionally, this protocol will serve as a control study for protocol # 90-M-0088.