Insulin's effects on SHBG (Sex Hormone Binding Globulin)

[Nssca]

How does insulin lower SHBG and is there any clinical studies available.

 

[KillerStack]

Don't know about the mechanism but to use insulin to lower shbg sounds like, to me, the worst reason to use the drug.

 

[KillerStack]

So I did a quick search on the mechanism and here's the first thing that popped up. Don't really know if this kind of info is useful to anyone here though.

J Clin Endocrinol Metab. 1995 Apr;80(4):1283-9.
Differential effects of insulin and insulin-like growth factor I on the production of plasma steroid-binding globulins by human hepatoblastoma-derived (Hep G2) cells.

Crave JC, Lejeune H, Brébant C, Baret C, Pugeat M.

Laboratoire de la Clinique Endocrinologique, Hôpital de l'Antiquaille, Lyon, France.

Changes in the plasma levels of corticosteroid-binding globulin (CBG) and sex hormone-binding globulin (SHBG) from birth to adulthood suggest that growth factors might influence clearance and/or hepatic secretion of CBG and SHBG in humans. The effects of insulin-like growth factor I (IGF-I) and insulin on CBG and SHBG synthesis by a clone of human hepatoblastoma-derived (Hep G2) cell lines were therefore investigated. The results showed that the immunoconcentrations of CBG and SHBG, as well as total protein concentration in culture medium from Hep G2 cells, were decreased by IGF-I and insulin. However, although the CBG-to-total protein ratio was decreased dose dependently by IGF-I and insulin, IGF-I and insulin did not dose-dependently decrease the SHBG-to-total protein ratio. The steady state levels of CBG and SHBG messenger RNAs (mRNAs) were reduced dose dependently by IGF-I with a half-effect at 5.4 +/- 1.9 and 4.6 +/- 1.6 nmol/L, respectively, and by insulin with a half-effect at 4.3 +/- 1.1 and 4.3 +/- 1.4 nmol/L, respectively. The maximum inhibitory effect of IGF-I on CBG mRNA level was 48 +/- 17% of control values and 60 +/- 13% for SHBG mRNA level. The changes in CBG mRNA levels were quantitatively similar to the changes in CBG immunoconcentration in the Hep G2 medium. In contrast, the inhibitory effects of insulin were only 17 +/- 8% and 31 +/- 12% of control values on CBG and SHBG mRNAs and 37 +/- 4% and 43 +/- 4% on CBG and SHBG concentrations, respectively. These results demonstrate that IGF-I reduces CBG and SHBG production by Hep G2 cells by decreasing mRNA steady state levels. The discrepancy between the inhibitory effects of insulin on CBG and SHBG mRNAs and protein secretion suggests that insulin exercises its inhibitory effects mainly on the mechanism(s) of translation and/or excretion of CBG and SHBG. The respective effects of IGF-I and insulin in the regulation of CBG and SHBG levels during fetal life and pubertal development in humans merit further study.

So basically insulin decreases synthesis of SHBG by reducing SHBG messenger RNAs. Something like that.

 

[Nssca]

Don't know about the mechanism but to use insulin to lower shbg sounds like, to me, the worst reason to use the drug.

I agree but I just remember DC and Phil and a few other more knowledgeable BB's say it helps... so was curious as what mechanisms was involved and how this may enhance a AAS cycle by freeing up bound Test.
Thanks

 

[KillerStack]

I agree but I just remember DC and Phil and a few other more knowledgeable BB's say it helps... so was curious as what mechanisms was involved and how this may enhance a AAS cycle by freeing up bound Test.
Thanks

Well, at the very least one should have their SHBG levels analyzed before using insulin to lower their supposed high SHBG. Don't treat something unless you know you have a problem.

I think most steroid users have low SHBG. Not to mention you could debate whether having semi-high SHBG is even a negative.

Impossible to know what your insulin gains were due to. To say you gain better with additional insulin due to lowered SHBG is a stretch to say the least. You might have a hunch or theory, but that's about it.

 

[Nssca]

My question isn't based on my hunch or theory but on what DC/phil and massive G have stated regarding insulins ability to free up bound test.
I would just like to know how and why this may be true.

 

[KillerStack]

My question isn't based on my hunch or theory but on what DC/phil and massive G have stated regarding insulins ability to free up bound test.
I would just like to know how and why this may be true.

Yeah I was just rambling in general about this since it has been mentioned here so many times.

And I have no problem with theories anyway, as long as it's not thought of as hard fact.

 

[joshbarnett]

a friend of mine was using nothing but insulin and his free test levels went up dramatically...his doctor couldnt believe or figure out why this happened so suddenly whether this is true for everyone i dont know but it did work for him...