The biopsy probably caused the temporary rise from 64 to 83 - as could a DRE, anal sex, etc. In the UK, you shouldn't have a PSA test for at least a couple of weeks after a biopsy.
Giving medication to see whether the PSA drops is a common first step (where the DRE indicates a large but benign prostate) in many countries, including the UK.
Heenan, I assume that he must have had two DREs for the doctors to tell him he had a large prostate?