The investigators will recruit 40 men between the ages of 40 to 80-years-old with low testosterone. Participants will be selected among those males referred to the Texas Tech University Health Sciences Center's (TTUHSC's) Internal Medicine Endocrinology Division outpatient clinic for the study and management of testosterone deficiency and to the TTUHSC Urology Department for diagnosis and management of prostate cancer that will result in testosterone deficiency due to surgical or pharmacological castration.