An increase of PSA in a low level of testosterone could set you as a HRPC patient (hormone refractory prostate cancer), but it all depends on the level of testosterone (T) and on the present HT protocol.
In another thread you have commented that you did RP in 2006 followed by chemo and RT, but you do not comment about the period you have been on HT. I presume you have stopped taking the drugs at some point so that they have lost their effectiveness in keeping low levels of T.
Such could be the cause of the rising PSA.
Are you still taking Lupron shots?
What have been the intervals of the shots?
In any case, the testosterone tests should have been measured along the period you have tested the PSA. The ultra sensitive PSA test will be insignificant to judge your cancer prognosis without other markers. I think it proper that you wait for your next PSA and T tests before deciding on anything.
Castrate levels varies from person to person and the use of T as a threshold to trigger a treatment varies according to the patient status. In a similar case as that of yours the castrate levels are taken at <10 ng/dl. Common thresholds for patients on HT are at <20 ng/dl but some guys have difficulty in getting levels lower than 30 ng/dl.
Some guys who have been on low T levels during long periods see it difficult to improve to normal levels at <300 ng/dl. Some guys take longer than a year since stopping HT drugs to see any substantial increase of the testosterone.
Before declaring a patient as HRPC, doctors usually change drugs or increase their potency. In case of failure patients are then moved to a “second line” HT drugs that act on intratumoral activity of cancerous cells.
There is no PSA velocity ruling the start of ADT3. You can start it whenever you and your oncologist decide.
You may do researches on the topic typing the sentence HRPC in a net search engine.
Hope for the best.