title: Combining testosterone and PDE5 inhibitors in erectile dysfunction: basic rationale and clinical evidences.
abstract: BACKGROUND
  Erectile dysfunction (ED) and decline of testosterone levels are frequently observed with age and also in illnesses with a common basis of endothelial damage.
  
  
  OBJECTIVE
  To review molecular mechanisms underlying androgen action upon its receptor and phosphodiesterase type 5 (PDE5) expression and regulation by testosterone in cavernous tissue and their clinical implication in the treatment of ED refractory to PDE5 inhibitors (PDE5-Is).
  
  
  METHODS
  From January 2003 to May 2006 [corrected] we performed an extensive, unsystematic MEDLINE literature search reviewing relevant data on basic and clinical studies regarding the efficacy of combination therapies.
  
  
  RESULTS
  Most trials using testosterone alone for treatment of ED in hypogonadal men suffer from methodologic problems and report inconsistent results, but overall the trials suggest that testosterone is superior to placebo. Orally effective PDE5-Is, such as sildenafil, tadalafil, or vardenafil, may be ineffective depending on the demonstration of testosterone regulation of PDE5 expression in human corpus cavernous, and their efficacy may be enhanced by testosterone adjunction whenever necessary.
  
  
  CONCLUSIONS
  Screening for hypogonadism in all men with ED is necessary to identify men with severe hypogonadism and some cases of mild to moderate hypogonadism, who may benefit from testosterone treatment. Identification of threshold values for testosterone supplementation to appropriately benefit from PDE5-Is failure may improve clinical management of unresponsive patients with minimization of unwanted effects.
authors.affiliation: Department of Medical Pathophysiology, University of Rome La Sapienza, 00161 Rome, Italy.
authors.forename: Emanuela A
authors.initials: EA
authors.lastname: Greco
authors.forename: Giovanni
authors.initials: G
authors.lastname: Spera
authors.forename: Antonio
authors.initials: A
authors.lastname: Aversa
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors* / Q000235:genetics; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D004359:Drug Therapy, Combination; D007172:Erectile Dysfunction / Q000188:drug therapy*; D006801:Humans; D008297:Male; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D016032:Randomized Controlled Trials as Topic; D013739:Testosterone / Q000627:therapeutic use*
chemical_list: D010726:Phosphodiesterase Inhibitors; D013739:Testosterone; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C517381:PDE5A protein, human