It is interesting that using low-dose Cialis does make my morning erections come back most days. Since that is the case, it seems like the other mechanisms involved in a morning erection (brain, nerves, signaling, venous closure, etc) are working, it's just a case of the body not generating enough nitric oxide during the morning erection process and that's where the PDE5 inhibitor comes into play, it allows you to make the most of the nitric oxide your body does produce. Does that seem right? If so, I am wondering if the decreased NO is hormonal or tissue related, hence the tests I wanted to run on myself.