Question about crashing e2 on trt

[Ch257]

Say in theory somebody is on exogenous testosterone and crashes their e2 with arimidex. Would this result in the production of LH even though they are on testosterone due to negative feedback (low estrogen)? Not that I would ever do that but just curious how the feedback loop would play into this

 

[Cataceous]

There are various considerations here. If this person has been on exogenous testosterone for a long time then a single, short-lived crash of estradiol is not going to be enough for an HPTA restart. If the AI dosing were continued indefinitely and if the exogenous testosterone doses were low enough then it is possible that some HPTA activity would be restored. It's complicated because both androgens and estrogens apply negative feedback to the hypothalamus, suppressing the production of GnRH. AI use can wipe out the estrogens, but the androgens may still keep things from working if levels are sufficient. At the pituitary only estrogens are suppressive. Therefore, if the pituitary receives GnRH and estrogen is low—or blocked with a SERM—then LH will be produced after a startup delay.

 

[Ch257]

There are various considerations here. If this person has been on exogenous testosterone for a long time then a single, short-lived crash of estradiol is not going to be enough for an HPTA restart. If the AI dosing were continued indefinitely and if the exogenous testosterone doses were low enough then it is possible that some HPTA activity would be restored. It's complicated because both androgens and estrogens apply negative feedback to the hypothalamus, suppressing the production of GnRH. AI use can wipe out the estrogens, but the androgens may still keep things from working if levels are sufficient. At the pituitary only estrogens are suppressive. Therefore, if the pituitary receives GnRH and estrogen is low—or blocked with a SERM—then LH will be produced after a startup delay.

How low would the estradiol have to be? Say the testosterone was always above 600 on exogenous test

 

[Cataceous]

I don't know. It's possible that if 600 ng/dL of serum testosterone is supplied exogenously then even zeroed-out estradiol wouldn't be enough to cause HPTA activity. But it's also possible that there would be some activity with low levels of estradiol. I can't think of any studies offhand that have created similar conditions.

 

[Ch257]

I don't know. It's possible that if 600 ng/dL of serum testosterone is supplied exogenously then even zeroed-out estradiol wouldn't be enough to cause HPTA activity. But it's also possible that there would be some activity with low levels of estradiol. I can't think of any studies offhand that have created similar conditions.

So tbh the reason I asked was because my total t raised since adding arimidex so I thought maybe some of it might be due to crashing my estradiol and not just conversion but rather Hpta. My e2 tested at 11 total t is 800. Been feeling shitty for a couple months so it’s probably been like this. Well for the sake of science before I cut out my AI I just went to test my LH to see and it came back undetectable so indeed your Hpta is still shut down even with crashed estradiol on trt

 

[Ch257]

So tbh the reason I asked was because my total t raised since adding arimidex so I thought maybe some of it might be due to crashing my estradiol and not just conversion but rather Hpta. My e2 tested at 11 total t is 800. Been feeling shitty for a couple months so it’s probably been like this. Well for the sake of science before I cut out my AI I just went to test my LH to see and it came back undetectable so indeed your Hpta is still shut down even with crashed estradiol on trt

Now we have some sort of scientific evidence supporting androgens alone will suppress Hpta to zero even without negative estradiol feedback

 

[Cataceous]

It's not clear why your total testosterone went up. If anything I'd expect the opposite. Blocking conversion of testosterone to estradiol spares a trivial amount of testosterone; with only 10 ng/dL of testosterone you can create 100 pg/mL of estradiol. On the other hand, crashing estradiol often lowers SHBG, which pushes down total testosterone on a fixed TRT dose.