• Changes in physical performance measured by an exercise testing regimen [ Time Frame: baseline and 6 months ] [ Designated as safety issue: No ]
  

• Changes in disability, fatigue, affect, and sense of well being assessed by validated questionnaires [ Time Frame: baseline, 3 months, and 6 months ] [ Designated as safety issue: No ]
  

The primary objective of this study is to determine whether testosterone replacement in older men, who have low testosterone levels and mild to moderate physical impairment, will increase their maximal voluntary muscle strength of major upper and lower extremity muscle groups. The second objective is to determine whether testosterone replacement will improve the power of knee extension, physical performance tests, the level of physical activity (measured by 3D accelerometer), self-reported disability, exercise tolerance and mobility. The third objective is to determine whether testosterone supplementation improves fatigue, affect, and overall sense of well being in older men with low testosterone levels. A fourth objective is to define the Minimum Clinically Important Differences in physical measures perceived by the participants (MCID).

Participant involvement will require 15-17 clinic visits over 28 weeks. Five to 7 of these visits are for physical testing, including body composition, muscle performance, and physical function. Throughout the study, hormone measurements will be obtained.

Inclusion Criteria:

• Community dwelling, ages 65 and older
• Self-reported difficulty in climbing 10 steps without resting, or difficulty in walking 2 or 3 blocks outside on level ground
• A score of 4 to 9 on the Short Physical Performance Battery (mild to moderate physical impairment)
• Total serum testosterone level (TT) < 350 ng/dL and > 100 ng/dL
• Without dementia (Mini-Mental State Examination [MMSE] score > 24)

Exclusion Criteria:

• Use of testosterone, anabolic steroids, dehydroepiandrosterone (DHEA), androstenedione or recombinant growth hormone (rGH) in the past year
• Alcohol or drug abuse
• Use of anti-convulsants or glucocorticoids (equivalent to prednisone > 20 mg/day)
• Prostate cancer, breast cancer or other cancers with life expectancy < 5 years
• Limiting neuromuscular, joint or bone disease, or history of stroke with residual neurological problems

• Any neurological condition that would impact cognitive functioning including:

  • epilepsy
  • multiple sclerosis
  • HIV
  • Parkinson's disease
  • stroke
  • other focal lesion
• Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) Axis I psychiatric disorder in past year or use of psychotropic medications in 6 months
• Abnormal prostate examination; PSA > 4 ng/mL; or BPH symptom score > 21
• Unstable angina, New York (NY) class III or IV congestive heart failure or myocardial infarction within 3 months of entry
• Abnormal laboratory values (at discretion of principal investigator)
• Untreated thyroid disease; systolic blood pressure > 160 or diastolic > 100 mm Hg
• Body mass index > 40 kg/m2
• Untreated severe obstructive sleep apnea