Does lower estrogen level increase or decrease liver hgh conversion to igf-1? So far what ive found is that lower estrogen levels are better (but not crashed levels)
Well, high estrogens lower IGF-I, but it does not follow that low estrogen levels increase it.
I'll describe the process by which T=[Aromatase]=>E2 negatively feeds back on IGF-I bioavailability:
E2 is a
negative factor for IGF-I bioavailability. That is, once aromatization is very high, E2 feeds back negatively on IGF-I levels because of
IGFBP-1, an IGF-I binding protein that is increased by estrogens and inactivates IGF-I in its active form.
E2, then, is not a positive factor for enhancing IGF-I. Rather,
aromatization as a process is.
Estrogens increase IGFBP-1, reducing IGF-I bioavailability and unleashing GH secretion by feedback withdrawal. It's why women have higher GH levels than men by body surface area and are less sensitive per-mg to rhGH, and require dose increase (titrating up) when using exogenous estrogens: oral estradiol dramatically decreases IGF-I activity, and transdermal less so.
The result of increasing E2 by T dose is a sort of asymptotic shape to the curve of
T/IGF-I in men. That is, at low levels of E2 (because low T & therefore aromatization), IGF-I activity is also low. As the E2 levels (because moderate/moderately-high T and therefore aromatization) increase, IGF-I does as well. Up to a point where E2 effects begin to inhibit (negatively feed-back on) IGF-I. Then the curve starts to taper off, increasing at a decreasing rate initially, and then negatively accelerating.
So, the task of maximizing IGF-I requires both the use of aromatizing androgen (e.g., T) and if using moderately-high/high/very-high T doses, then
also using an aromatase inhibitor (AI) at a dose that doesn't totally abrogate (block) aromatase but rather shifts the inflection point (asymptote) to the right on the
T/IGF-I curve. Moreover, AI compound selection is paramount. Exemestane does not directly decrease IGF-I (because its primary active metabolite is an androgen & it possesses a steroidal core), so it is a good choice for this task.