Dan-
178 is indeed low. Do you know what your testosterone was in the past?
I never had my T level measured until recently (15 months after LRP). My score was 350 (bottom of the "normal" range), and subsequently had bone density measured - and found that I have low bone density in my lumbar spine (which can be caused by low T).
First thing I did (based on advice from someone on HW) was to read Dr. Abraham Morgentaler's book
Testosterone for Life. Very good book, and specifically addresses the issue of testosterone replacement therapy for guys who were treated for PCa.
Then, I had an appointment with Dr. John Mulhall. He told me that his hospital (Sloan Kettering) has never seen a single instance of a guy with consistently zero PSA having his PSA go up after beginning therapy to raise testosterone level. (His sample size is only around 150 men, so not large enough to be conclusive proof, but large enough to make him confident that the risks are minimal to proceed with TRT or similar.)
I also discussed with Dr. Mulhall whether prostate removal can impact T level. Surprisingly (to me), Dr. Mulhall said that some men who had prostate removal do experience a sudden drop in T levels - but the reason is not yet understood. He suggests that men get their T level measured (total T and free T) prior to surgery so they have data to compare against when they have the levels measured again after surgery.
-Gedman