15 pre-menopausal women will be asked to volunteer for a follow up study. For 5 months, pre-menopausal women in this study will receive monthly injections that contain a study drug (leuprolide) that reduces estrogen to postmenopausal levels. This drug is approved by the FDA to reduce estrogen for the treatment of uterine fibroids and endometriosis, but is not approved for use in healthy women. In this study, the drug is being used to decrease hormones to determine if this reduces brown fat activity. 6 months after the first injection, these women will be asked to repeat the PET/CT studies.