The purpose of the study is to determine the effects of testosterone treatment on erectile function, fatigue, depression, cognitive function, quality of life, urinary incontinence, pain, and damage to neurons in male Multiple Sclerosis patients with low testosterone, using questionnaires, blood samples and a rectal exam in volunteers 55 years and older.

Volunteers will be treated weekly with Xyosted 75 mg (given subcutaneously) for 3 months during which they will have 3 study visits, 6 weeks apart. The Baseline visit will include providing a blood sample, completing questionnaires, receiving training on the Xyosted auto-injector, and undergoing a rectal exam for participants 55 years and older. Visits 2 and 3 will also include collecting a blood sample and completing questionnaires. At Visit 3, the rectal exam for those age 55 years and older will be repeated.

Inclusion Criteria:

• Males, age 18 years and older, with a definite diagnosis of multiple sclerosis.
• Low testosterone (<300 ng/dl) on two successive blood draws before 9:00 am
• Not in an intercurrent relapse.
• Sexually active.
• Have subjective complaints about erectile function and libido.
• Must be willing and able to get labs drawn, complete questionnaires (BDI, MFIS, MSNQ, SDMT, MSQOL, ADAM, AUASS, SHIM, MSHQ, ICIQ, UDI, IIQ, MPQ) and commit to site visits schedule.

Exclusion Criteria:

• Males unable to fulfill the above criteria and all female patients.
• Males who have been on sex hormone treatment including androgens, estrogens, or anti-estrogens for hypogonadism or other medical condition during the 12 months prior to study.
• Males who have taken dehydroepiandrosterone (DHEA) during the 3 months prior to study.
• Patients who are taking anticoagulants or have thrombosis, serious cardiac, pulmonary, renal, gastrointestinal, hepatic, immunologic, infectious, neoplastic (with particular focus on patients with known or suspected estrogen or testosterone-dependent tumors), urologic disease especially prostatic hypertrophy/nodules and testicular mass, or insulin-dependent diabetes.
• Patients with an abnormal prostate as evidenced by known history of prostatic disease, symptoms suggestive of prostatic disease or elevated levels of prostatic specific antigen (PSA 4 ng/ml or higher) measured within the last 12 months.
• Patients with history or complaint of testicular mass.
• Patients with hematocrit greater than 50%
• Patients with major psychiatric illness
• Patients with active alcoholism.
• Patients with a history of drug abuse within the past five years.
• Patients with BMI ≥ 35
• Patients with generalized skin disease that may affect absorption of testosterone (e.g. psoriasis) or a known skin intolerance to alcohol.
• Patients with history of pituitary disease.
• Patients with a cholesterol level greater than 300 mg/dl.
• Patients who are receiving or have received experimental therapies in the six months preceding enrollment.
• Patients who have history of positive titers to Human Immunodeficiency Virus (HIV)1 and 2; HTLV1; or Venereal Disease Research Laboratory (VDRL).
• Patients who have clinical evidence of Lyme disease.
• Males who are trying to get their partner pregnant.
• Patients on Finasteride
• Patients who are mentally or emotionally incompetent in the opinion of the examining neurologist or unable to give informed consent, or to understand and comply with the study protocol.
• Any other contraindications according to the manufacturer's exclusion criteria.