Foible No. 6. Certain drugs have a profound effect on serum PSA levels.
Most prominent of such drugs are the 5 alpha-reductase inhibitors (5ARIs),
finasteride (Proscar)and dutasteride (Avodart). These 2 drugs deprive the
prostate of dihydrotestosterone (DHT), its main nutrient, and shrink the gland,
thus improving urinary flow and decreasing symptoms in many men with BPH.
Propecia, a low dose form of Proscar used to prevent hair loss, acts similarly.
The effect on prostate epithelium is especially dramatic (see graphics, above Left).
Continued usage of these drugs causes serum PSA levels to decrease by some 50%, gradually
over a period of months or years (see chart, above Right). Thus, a time-dependent
effect of drugs is another variable that confounds serum PSA levels (Foible 6).