GnRH-a for Ovarian Protection During CYC Therapy for Rheumatic Diseases

1. Female, post menarche, not menopausal 2. Ages 18-40 years inclusive at enrollment 3. Diagnosis consistent with a rheumatic or autoimmune disease requiring 3-6 months of daily or intermittent cyclophosphamide therapy. This may include, but is not limited to: * Systemic lupus * Sjogren's syndrome * Systemic vasculitis * Isolated vasculitis of the central nervous system * Other autoimmune neurologic diseases requiring cyclophosphamide including transverse myelitis, peripheral neuropathies, multiple sclerosis, neuromyelitis optica, and retinal vasculitis * Behcet's syndrome * Scleroderma * Inflammatory myositis * Interstitial lung disease, other autoimmune pulmonary diseases requiring cyclophosphamide * Overlap connective tissue diseases not precisely fitting the above definitions clearly requiring cyclophosphamide for severe immune mediated organ damage * Rheumatoid vasculitis 4. Patients will have planned cyclophosphamide treatment according to any one of the following regimens: * 3 to 6 months of daily oral cyclophosphamide: Lupron/placebo must be given within four (4) weeks of initiation of daily cyclophosphamide. * The Eurolupus regimen consisting of 6 fortnightly biweekly boluses of 500 mg cyclophosphamide: First dose of Lupron/placebo must be given 10 days prior to the second dose of cyclophosphamide * 3 to 6 monthly boluses of cyclophosphamide by the NIH regimen: First dose of Lupron/placebo must be given 10 days prior to the second dose of cyclophosphamide 5. A satisfactory plan for contraception consistent with cyclophosphamide administration (when appropriate: depot progestins, IUD, combination oral contraception and/or dual barrier contraception). Exclusion Criteria: 1. Symptoms consistent with ovarian failure based on gynecologic evaluation and confirmatory laboratory testing 2. Prior unilateral or bilateral oophorectomy 3. Cervical intraepithelial neoplasia (CIN 2, or more severe), that has not been adequately evaluated or is not being adequately treated 4. Contraindications to use of GnRH-a (e.g., undiagnosed abnormal uterine bleeding) 5. Prior adverse or allergic reaction to GnRH-a 6. A history of severe psychiatric disorders, particularly severe depression that is currently not adequately treated 7. History of significant noncompliance with medical treatment 8. Patients with major risk factors for decreased bone mineral content such as chronic alcohol and/or tobacco use, strong family history of osteoporosis, or chronic use of drugs that can reduce bone mass such as anticonvulsants that have not already been addressed with appropriate measures to preserve bone mass. 9. Pregnant or breastfeeding 10. Significant thrombotic event requiring treatment that will not have received appropriate therapy for at least 4 weeks before initiation of study drug.