Women undergoing myeloablative allogeneic hematopoietic cell transplant (MA HCT) will receive GnRH agonist leuprolide. Women undergoing reduced intensity allogeneic (RIC) HCT will be observed.

This study is to use gonadotropin releasing hormone (GnRH) agonist leuprolide prior myeloablative hematopoietic cell transplantation to prevent ovarian dysfunction in post-menarchal women. The primary objective is to determine the effect of GnRH agonists on the incidence of ovarian failure. The secondary objectives are * to determine how effective GnRH agonists are at suppressing menses during * to determine the incidence and timing of resumption of menstrual cycles after HCT * to determine the incidence and timing of resumption of normal FSH and LH levels after HCT * to determine the incidence of normal AMH levels after HCT * to determine the effect of GnRH agonists on immune reconstitution after HCT * to assess the safety and tolerability of GnRH agonists in the context of HCT A total of 47 patients will be accrued in this study.