This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The primary objective of Effects of Testosterone Replacement in Men with Erectile Dysfunction and Low Testosterone Levels Who Are Receiving a Selective Phosphodiesterase Inhibitor is to determine whether testosterone supplementation in ethnically diverse men with erectile dysfunction (ED) and low testosterone levels improves response to a selective phosphodiestrase-5 inhibitor. This study will test the following hypotheses: 1) Testosterone replacement in men with erectile dysfunction and low testosterone levels augments response to sildenafil citrate by improving erectile function, stimulating spontaneous sexual thoughts and sexual desire, and improving well-being; and 2) In comparison to placebo, testosterone replacement is associated with greater improvement in penile rigidity in response to administration of sildenafil citrate because of testosterone s multiple actions, including its trophic effects on the mass of ischiocavernosus, bulbospongiosus, and cavernosal smooth muscles, and its stimulatory effects on penile nitric oxide synthase enzyme. The study has the following specific aims:
Specific Aim #1 : To determine if testosterone supplements improve erectile function, quality of life and partner satisfaction for patients in an ethnically diverse population who receive both testosterone and PDE-5 inhibitor as compared to patients taking PDE-5 inhibitor alone.
Specific Aim #2 : To assess cavernosal smooth, bulbospongiosus, and ischiocavernosus muscles size by MRI scan in patients in an ethnically diverse population who receive testosterone and PDE-5 inhibitor as compared to patients taking only PDE-5 inhibitor. This study will be a double-blind, placebo-controlled, parallel-group, randomized clinical trial in men, 40-70 years of age, who present with mild to moderate erectile dysfunction and have serum total testosterone levels below 350 ng/dL. After a four-week control period, the eligible men will be randomly assigned to receive either a standardized dose of sildenafil citrate (50 mg) plus a placebo gel or sildenafil citrate plus a replacement dose (100 mg daily) of testosterone gel. The proposed study will have a great impact on the health and quality of life in 60 men who have ED with low serum testosterone levels. We anticipate that testosterone administration in men with low testosterone levels will improve libido and sexual activity, increase lean body mass, and improve both bone mass and overall sense of well-being. Improved erectile function and penile rigidity will lead to successful sexual intercourse, improving self-esteem, personal and partner satisfaction, and quality of life. This study will allow researchers to better understand the physiology of ED, thereby allowing them increased ability to provide proper treatment. This study also will lead to better understanding of the ED mechanism, particularly the role of testosterone on the erectile-participating muscles.
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