IMHO some sales ads, have been miscommunicating, causing a common misconception that a 19-Nor is gyno proof. That is so very far from the truth, a 19-Nor is NOT gyno proof, it is a different kind of gyno.
Although 19-Nors do not convert to estrogen directly, 19-Nors can cause a different type of gyno that is caused by progesterone. Progesterone gyno doesn't cause a lump like normal gyno. Typically your nipples start to itch/burn and then a few weeks later you start to make milk/prolactin.
In the past, I have successfully stopped this at the itchy stage.
I used B6 and Vitex at way over the recommended dosage, which minimally helped, but did NOT solve the issue. Only the letro and caber worked completely and stopped it dead in it's tracks.
I was previously using Letro at 1mg ED, but I was told Letro may hinder gains. From my understanding, if the Letro lowers the estrogen too much, that will hinder gains. Therefore I decreased the Letro to 0.5mg ED and have not had any gyno issues. Next week I will try decreasing the Letro to 0.25mg ED and see how that works.

onder:
I am currently on a 19-NOR cycle. Today this is my prevention cycle.
B6 100mg ED
Vitex 500mg ED
Letro 0.5mg ED (Next week 0.25mg ED)
Cabergoline 0.15mg ED
IMHO: (my experience)
I am 19-NOR/Progesterone gyno sensitive.
Cabergoline is a must for me. Still testing as to if the Letro is a must.
The B6 and Vitex are only minimally effective, and not able to be used alone.
Grega