T Nation

Does SHBG Inflate E2 Readings?


#1

We all know high SHBG inflates total testosterone. That is, your total may measure high while free T is midrange (or midrange and low, respectively). My SHBG and E2 (Labcorp sensitive test) are both high. I’m wondering - is my E2 actually high, or is most of it bound to SHBG, leaving proportionally less “free” E2?

Basically I’m trying to decide whether to up my anastrozole, or attack my SHBG (tongkat, more carbs, etc.).


#2

My SHBG is generally high, and often above range, but my E2 tends to be fairly low. The highest reading I’ve seen is 80 nmol/L, which is around 20 ng/dL (I think).

But that’s purely anecdotal. I’d be interested to hear if anyone has data.


#3

Per wikipedia:

The relative binding affinity of various sex steroids for SHBG is dihydrotestosterone (DHT) > testosterone > androstenediol > estradiol > estrone.[4] DHEA is weakly bound to SHBG as well, but DHEA-S is not.[4] Androstenedione is not bound to SHBG either, and is instead bound solely to albumin.[5]

So we can expect a smaller effect with E2 than with T. And if you feel good with that E2 – which as I understand it is near optimal – it suggests the binding affinity is negligible.

I’ll experiment with the anastrozole.

Interestingly, my DHT is on the low end. I wonder if that’s because SHBG is binding it all up.


#4

So while we are greatly concerned with T+SHBG which is tightly bound, T+E2 is not. So total E2 is active and what we need to focus on. So while elevated SHBG will reduce free E2, total E2 is what you need to focus on.

[When on TRT with high range TT and FT, E2=22pg/ml - 80 pmol/L is optimal for most guys.]