Symptoms relating to low testosterone levels include erectile dysfunction, reduced erectile quality, diminished nocturnal erections, increase in abdominal and visceral adipose tissue. Physical symptoms relating to fatigue, decreased vigor and diminished strength, reduced muscle mass, reduction of lean muscle mass, and decreased in bone mineral density. Sexual symptoms include diminished libido, diminished sexual activity, diminished quality of erection and weakness in ejaculation, and limited quality of orgasm. Psychological symptoms include mood changes, impaired concentration, diminished motivation, reduced memory, decline in libido, and depression. Low testosterone levels in the aging male may contribute to the development of several comorbid conditions. Examples of these conditions are myocardial infarction, coronary atherosclerosis, type 2 diabetes, obesity, hypertension and osteoporosis.