Estra-4,9 was purported by its makers to be a precursor to trenbolone. However, as you can see, this molecule lacks a double bond in the 11 position. There is no process in the body that would produce this double bond. This prohormone is actually a precursor to dienolone. It is unknown how well this PH will convert. As a dione, it would require conversion at the C-17 position by 17 beta hydroxysteroid dehydrogenase, which does not seem to be an efficient conversion for PH’s. This being said, estra-4,9 has a favorable anabolic to androgenic ratio with about equal anabolic activity to testosterone but only one tenth the androgenic activity. This prohormone cannot convert to estrogenic metabolites through aromatization but likely converts to less potent 5-alpha reduced metabolites like other nortestosterone derivatives. Like other prohormones, estra-4,9 has a very short half-life and requires fairly large and frequent doses to maintain plasma levels necessary for an anabolic effect. Also, since this prohormone is a nortestosterone derivative it likely results in significant shutdown of natural testosterone production and since it has minimal androgenic activity will likely result in decreased libido and may induce gynecomastia through disruption of the estrogenic/androgenic ratio.
Some have invoked progesterone to be a cause of gyno with the use of this compound. As the progesterone receptor binding of this prohormone (and of dieneolone) is quite low and the fact that activation of the progesterone receptor likely does not cause gyno, PR binding is unlikely to be the cause.