Testosterone Replacement Therapy in Advanced Chronic Kidney Disease

Inclusion Criteria: Inclusion criteria: CKD subjects; males with calculated GFR (MRDR equation) between 15 and 40 ml/min/1.73m2 and stable or slowly progressive renal failure (decline in function of \<1ml/min/month) including those patients requiring hemodialysis and serum testosterone levels of \<300 ng/ml and capable of safely performing required exercise testing and serum testosterone levels of \<300ng/ml and capable of safely performing required exercise testing.

Exclusion Criteria: Exclusion criteria: applicable to both CKD and control subjects. Any unstable chronic medical condition, previous kidney transplant. Uncontrolled diabetes mellitus, active vasculitis, active autoimmune disease, malignancy(\<5 yrs), obesity (BMI \> 35), alcoholism or other recreational drug use, active heart disease, angina, uncontrolled arrhythmias or myocardial infarct within past 3 months, peripheral vascular disease with claudication, active lung, liver or GI disease, sleep apnea, medically unstable subjects and subjects who received anabolic, catabolic or cytotoxic medications during the prior 3 months. History of prostate CA, PSA \>4g/ml, or advanced BPH (AUA symptom score \> 21) and abnormal prostate on digital rectal examination. Bone or joint abnormalities that would preclude exercise testing.