The most recent and comprehensive study I've found on deca says the following:
Estrogen-sensitive nandrolone users have always complained about inexplicable estrogen-like symptoms that cannot be treated with conventional anti-estrogen therapies.
One theory blamed a feminizing hormone called prolactin. However that theory never really held up since potent androgens tend to decrease prolactin and prolactin sensitivity whereas estrogens seem to increase its activity. There was also no evidence to assume that prolactin played any significant role in the most common of estrogenic side-effects in the absence of estrogen, which would fail to explain why conventional anti-estrogenic therapy did not work with nandrolone use/abuse, given that nandrolone aromatized considerably less and blood profiles of users generally showed low estradiol and estrone levels in the blood after several weeks of use. Fortunately this theory was only shortlived, and only maintained by a few obscure guru’s eager to draw attention to themselves by claiming to have found a solution, where there wasn’t a problem.
Another theory, that has persisted very long, and remains the most popular belief today was that nandrolone’s progestational activity lay at the base of the perceived estrogenic effects. This theory again held very little ground, but is commonly accepted because it was never thoroughly refuted since the rumour first started circulating. Indeed, nandrolone3 and several of its metabolites4,5 have been identified as being progestins. Meaning they can bind and activate the progesterone receptor. And equally supportive of the theory, studies have demonstrated that progestagenic activity can both stimulate and suppress estrogenic activity6. Whether that holds true for the more common estrogenic side-effects is not really known, but it leant a validity to this theory. However, again, progestins have never been shown to cause estrogenic side-effects in the absence of estrogen. So once again, this did not account for the lack of effect with conventional anti-estrogens.
A third and last theory that has only been circulating of late is that nandrolone was directly estrogenic, binding and activating the estrogen receptor (ER) without metabolizing. Most likely the rumour initiated after the proposed theory that oxymetholone, another non-aromatizing drug, may me directly estrogenic. It was a theory first proferred by Bill Llewellyn7, and found support with people like myself and organic chemist Patrick Arnold. A dutch pseudo-guru even suggested he had found proof in the fact that studies demonstrated that nandrolone bound the estrogenic receptor8. This infamous study however demonstrated that nandrolone had a more estrogenic effect at the ER than testosterone in millimolar doses. However testosterone is not a potent ER activator, nor are millimolar in vitro doses indicative of what a typical steroid user would have in his blood.
All of these theories were shot down by two other studies9,10. The first study is not immediately relevant, but that it contained a table with results from an older study, showing the relative estrogenic properties of several progestins, compared to estradiol.
As you can see from the table above, taken from that study, nandrolone was about 60% as estrogenic in nature as estradiol itself. So far nothing special. All this tells us is that nandrolone has very potent estrogenic action that cannot be explained by aromatization, which is what we already knew. At best this has some shock value by demonstrating just HOW estrogenic it really is. The second study however was undertaken by the same researchers to hopefully shed some light on the situation. It did not. But it disproved all commonly accepted theories supported to date. In the study the researchers administered nandrolone with either an aromatase blocker, a progesterone receptor blocker or an estrogen receptor blocker. As was to be expected the aromatase blocker had no effect whatsoever on the estrogenic activity of nandrolone. More surprisingly, neither did the progesterone receptor blocker. Which also strikes a blow for basically any involvement of progestational activity in the development of common estrogenic side-effects associated with AAS use. And lastly, and even more surprisingly, the estrogen receptor blocker’s effect on the estrogenic activity was just barely significant. This suggests that nandrolone’s direct binding (or that of its metabolites) to the estrogen receptor played a very limited role. At the end of that all we could state was that nandrolone was 60% as estrogenic as estradiol itself, but more than 55% of that could not be explained.
Yours truly dug a little deeper and actually found the answer in a synthetic nandrolone metabolite, named estren (19-Nor-4-androstene-3?,17?-diol)11. Estren was found to only weakly bind the estrogen receptor, showing no real activity at that site and possessing a 300-fold lower binding affinity. Yet it mimicked the actions of estrogens in osteoblasts. Estren was however shown to be as active as DHT at activating certain androgen receptor related transcripts. The same study also demonstrated that estren was capable of activating estrogen specific constructs in the DNA through the androgen receptor. Estren is a metabolite of nandrolone through the 3?-HSD enzyme. So in first instance one might suggest we start looking for something that blocks this enzyme. However I mentioned that this steroid was synthetic. Nandrolone is a natural androgen. So why does estren not appear naturally in the body ? Well mostly because it is a very labile structure, that is quickly converted back to nandrolone. The problem however is that the researchers noted that despite similar activity on several constructs as DHT, it bound with a 200-fold lower activity to the androgen receptor. The researchers found that the high androgenic potency of estren resulted in its conversion to the more stable molecule nandrolone, almost 50% in 4-6 hours, and no less than 95% within 24 hours. From this it can be concluded that the effects of estren via the AR are mediated by its metabolite nandrolone, and it is in fact nandrolone that activates estrogen specific transcripts via binding and activating the androgen receptor. Now the study also noted that binding of DHT activated estrogen-related transcripts, so this is not uncommon, but DHT did so with a 30 to 100-fold lower potency than estren. The authors concluded :
“Finally, the unexpected estren-dependent activation(and by extension nandrolone-dependent activation) of ERE-driven gene expression in cells that express AR, which occurs with far greater potency relative to DHT, predicts the possibility of some troublesome feminizing effects in males, which still await examination."
I have used just about every AAS there is, more than once. I cannot, by way of personal experience, say that Nolva has produced the effects you, and others, say will occur due to a theory based on studies done on women post cancer treatment. So to answer your challenge, I have done just that, and did not see the dire results predicted, and I attribute that to the studies quoted above. I don't think there are enough clinical studies out there to make a sweeping statement like that.