This reversible binding blocks the release of LH and FSH from the pituitary. The reduction in LH subsequently leads to a rapid and sustained suppression of testosterone release from the testes and subsequently reduces the size and growth of the prostate cancer. This in turn results in a reduction in prostate-specific antigen (PSA) levels in the patients blood. Measuring PSA levels helps to monitor how patients with prostate cancer are responding to treatment.Unlike GnRH agonists, which cause an initial stimulation of the hypothalamic-pituitary-gonadal axis (HPGA), leading to a surge in testosterone levels, and under certain circumstances, a flare-up of the tumour, GnRH antagonists do not cause a surge in testosterone or clinical flare. Clinical flare is a phenomenon that occurs in patients with advanced disease, which can precipitate a range of clinical symptoms such as bone pain, urethral obstruction, and spinal cord compression. Drug agencies have issued boxed warnings regarding this phenomenon in the prescribing information for GnRH agonists. As testosterone surge does not occur with GnRH antagonists, there is no need for patients to receive an antiandrogen as flare protection during prostate cancer treatment. GnRH agonists also induce an increase in testosterone levels after each reinjection of the drug – a phenomenon that does not occur with GnRH antagonists such as degarelix.GnRH antagonists have an immediate onset of action leading to a fast and profound suppression of testosterone and are therefore especially valuable in the treatment of patients with prostate cancer where fast control of disease is needed.
Type 3, however, can be uniquely identified, since 
  
    
      
        X
      
    
    {\displaystyle X}
   and 
  
    
      
        Z
      
    
    {\displaystyle Z}
   are marginally independent and all other pairs are dependent. Thus, while the skeletons (the graphs stripped of arrows) of these three triplets are identical, the directionality of the arrows is partially identifiable. The same distinction applies when 
  
    
      
        X
      
    
    {\displaystyle X}
   and 
  
    
      
        Z
      
    
    {\displaystyle Z}
   have common ancestors, except that one must first condition on those ancestors.