Does nandrolone activate progesterone receptors?

[benaoao]

Do you have a source for this? Nandrolone has a lower affinity for the progesterone receptor than progesterone, which reduces its relative activity. But I've so far found nothing saying that the effect after binding is weaker. The relatively large doses of nandrolone seem sufficient to promote normal and above progestogenic activity.

Quantifying the net effect is tricky and you’d need to look at animal studies for that. Exemple here, table 3:

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2605.1978.tb00015.x

It’s consistent with this text that says that nandrolone is 10x more progestogenic than testosterone but T is 100x weaker than progesterone.

Nandrolone - an overview | ScienceDirect Topics

www.sciencedirect.com

19-Nortestosterone (19-NT or nandrolone) is a long-acting ester with potent androgenic effects and a high progestational activity (10 times that of T)

And also consistent with anecdotal use of E2 with Deca: guys need to be veryyyyy cautious with how much E2 they inject. Otherwise it’s gyno territory.

 

[Gman86]

The idea is that nandrolone is competing with endogenous progesterone to bind at the progesterone receptors. It only has 20% or so of the binding affinity of progesterone, but in sufficient amounts it would be displacing some progesterone from the receptors. If nandrolone activates the progesterone receptor as much as progesterone then the displacement of progesterone doesn't matter in terms of overall activity. But if nandrolone is weaker than progesterone in receptor activation, as claimed by @benaoao, then it's possible for overall progestogenic activity to be reduced. However, sources such as Wikipedia refer to nandrolone as "a potent progestogen", and also list it as a PR agonist without qualification.

Furthermore, there are anecdotal reports that some guys who take only nandrolone supplement with estradiol. You'd think that would not be a viable strategy if nandrolone were already increasing estrogenic activity.


Yes, I think this is likely. Of course this assumes there's not additional suppression of endogenous progesterone caused by the nandrolone. Otherwise, assuming nandrolone is a full agonist of PR, then you could multiply the weight of the nandrolone you're taking by some factor, maybe 20%, and view that as the equivalent amount of progesterone you're getting.


I have seen that post, which says that vitamin E can antagonize estrogen receptors, inhibit aromatase, and also down-regulate aromatase expression. Of course it also says that "Vitamin E reduced androgen signaling without affecting androgen metabolism." This could be counterproductive.

Interesting about vitamin E possibly downregulating androgen signaling, was watching a video last night where he goes over a study that basically says the opposite. It was saying that vitamin E reduced prolactin, and anytime something reduces prolactin, while being natural, ur usually going to see an increase in gonadotropin releasing hormone, and theoretically an increase in LH and FSH, not a downregulation. We all know increased prolactin while natural will downregulate androgen production, but I don’t think I’ve ever seen a study showing that vitamin E increased prolactin, only studies showing it has the potential to reduce prolactin, same with estrogen, so I’m curious what mechanism vitamin E downregulate androgen signaling through, if that’s true

And in regards to nandrolone possibly suppressing endogenous progesterone activity, in this podcast around the 47 min mark I think, Haidu starts talking about progesterone and preg and how they are 2 of the very few hormones where taking exogenous forms of them does not suppress endogenous production, even at extremely high doses. It’s actually the opposite, according to him. He says they are 2 of the very few hormones where taking them exogenously actually promotes endogenous production. So assumjng this is true, and we know that nandrolone is a progesterone agonist, would that mean that nandrolone theoretically wouldn’t suppress endogenous progesterone production either?

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[Cataceous]

...
It’s consistent with this text that says that nandrolone is 10x more progestogenic than testosterone but T is 100x weaker than progesterone.
...

These factors are referring to a comparison by weight, and are therefore consistent with the differences in relative binding affinities. Is there any evidence for less progestogenic activity besides that one parameter in one experiment on rabbits?

...He says they are 2 of the very few hormones where taking them exogenously actually promotes endogenous production. So assumjng this is true, and we know that nandrolone is a progesterone agonist, would that mean that nandrolone theoretically wouldn’t suppress endogenous progesterone production either?
...

Seems doubtful. As we saw with the guy on 300 mg per week of nandrolone, full HPTA suppression is achieved, which means you lose an important signal for progesterone production.