Review

Asian Journal of Andrology (2006) 8, 3–9; doi:10.1111/j.1745-7262.2006.00105.x

Recent insights into androgen action on the anatomical and physiological substrate of penile erection

Louis J G Gooren1 and Farid Saad2,3

  1. 1Department of Endocrinology, Andrology Section, Vrije Universiteit Medical Center, 1007 MB Amsterdam, The Netherlands
  2. 2Gulf Medical College, Medical University of the United Arab Emirates, 2563 Ajman, UAE
  3. 3Andrology Department, Schering AG, 13342 Berlin, Germany

Correspondence: Prof. Louis J. G. Gooren, Department of Endocrinology, Andrology Section, Vrije Universiteit Medical Center, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands. Fax: + 31-20-444-0502. E-mail: ljg.gooren@vumc.n1

Received 30 August 2005; Accepted 24 October 2005.

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Abstract

Erectile response is centrally and peripherally regulated by androgens. The original insights into the mechanisms of action of androgens were that androgens particularly exert effects on libido and that erections in response to erotic stimuli were relatively androgen-independent. It was shown that sexual functions in men required androgen levels at the low end of reference values of testosterone. So it seemed that testosterone was not useful treatment for men with erectile difficulties, particularly following the advent of the phosphodiesterase type 5 (PDE5) inhibitors. However, approximately 50 % of those treated with PDE5 inhibitors discontinue their treatment. A number of recent developments shed new light on testosterone treatment of erectile dysfunction (ED) in aging men. (1) A recent insight is that, in contrast to younger men, elderly men might require higher levels of testosterone for normal sexual functioning. (2) Several studies have indicated that PDE5 inhibitors are not always sufficient to restore erectile potency in men, and that testosterone improves the therapeutical response to PDE5 inhibitors considerably. (3) There is growing insight that testosterone has profound effects on tissues of the penis involved in the mechanism of erection and that testosterone deficiency impairs the anatomical and physiological substrate of erectile capacity, reversible upon androgen replacement. The synthesis of PDE5 is upregulated by androgens, and the arterial inflow into the penis is improved by giving androgen. The above invites a re-examination of the merits of giving testosterone to aging men with ED. The beneficial effects of PDE5 inhibitors may only be optimally expressed in a eugonadal environment.

Keywords:

testosterone, erection, corpus cavernosum, phosphodiesterase type 5 inhibitors

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