EQ, primo, Dbol and aromatisation

[dr. Doping]

As it's pretty well known at this point, primo and EQ somehow inhibit aromatisation. Dr. Todd Lee, a doctor, biochemist and IFBB pro has repeatedly said, it's due to their structure, because they both have a double bond at position 1. But Dbol also has a double bond at that position and differs from EQ by only having the methyl group at position 17. Therefore, I am wondering, how exactly do EQ and primo inhibit aromatase? Does the 17-alpha methyl group somehow offset the double bond at position 1?

Images of the structures of test, primo, EQ and Dbol:
test:

primo:

Boldenone (no ester):

Dbol:

 

[dr. Doping]

It appears I have found out why: the methyl group at position 17 changes the orientation of the steroid when interacting with the aromatase enzyme. The same trend can be observed with nandrolone: anabolics 11th edition (by William Llewellyn) cites nandrolone as mildly estrogenc, methyl nandrolone as moderately and ethyl nandrolone as strongly estrogenic.

 

[Donvitosharkone]

It appears I have found out why: the methyl group at position 17 changes the orientation of the steroid when interacting with the aromatase enzyme. The same trend can be observed with nandrolone: anabolics 11th edition (by William Llewellyn) cites nandrolone as mildly estrogenc, methyl nandrolone as moderately and ethyl nandrolone as strongly estrogenic.

Indeed!


Both Primo (Methenolone) and EQ (Boldenone) share that 1,2-double bond modification in their A-ring. That alteration makes the molecule less prone to aromatization compared to plain testosterone, because it changes how the substrate fits into the aromatase enzyme. In simple words, aromatase doesn’t “grab” these compounds as efficiently, so conversion into estrogen drops. That’s why guys can run them at solid doses and not see the same kind of water retention or gyno risk as they would with test.


Now, the confusion kicks in with Dbol (Methandrostenolone), because yeah, it also carries the 1,2-double bond. On paper, you’d expect it to be low aromatizing like EQ.

But like you found out, the key difference: Dbol is 17-alpha methylated. That methyl group makes the compound orally active but also completely changes the way aromatase interacts with it. The 17-aa structure doesn’t cancel out the 1,2 double bond, but creates a new binding dynamic where aromatase actually converts it pretty aggressively into a unique estrogenic metabolite (17α-methylestradiol). That metabolite is way more potent at the receptor than regular estradiol, which is why Dbol blows guys up with water and gyno issues despite the same “structural feature” as EQ.


Structure matters, but context matters more. You can’t just look at one modification in isolation. EQ and Primo carry that 1,2-double bond and no 17-aa, so they come out clean. Dbol has both, and the methyl group forces a different pathway where estrogenic activity gets amplified, not suppressed.

Thanks for bring in this interesting topic!!

@ThePedsFather comments?

 

[dr. Doping]

But like you found out, the key difference: Dbol is 17-alpha methylated. That methyl group makes the compound orally active but also completely changes the way aromatase interacts with it. The 17-aa structure doesn’t cancel out the 1,2 double bond, but creates a new binding dynamic where aromatase actually converts it pretty aggressively into a unique estrogenic metabolite (17α-methylestradiol).

Structure matters, but context matters more. You can’t just look at one modification in isolation. EQ and Primo carry that 1,2-double bond and no 17-aa, so they come out clean. Dbol has both, and the methyl group forces a different pathway where estrogenic activity gets amplified, not suppressed.

Exactly. And the trend seems to be somewhat consistent with other groups at 17a position and other steroids. Very interesting and something to keep in mind when trying to understand how steroids work (for example, why masteron is NOT an AI and possibly just antagonises estrogen receptor alpha at higher doses).