SHBG Background Information

[Youthful55guy]

I was curious about the half life of Sex Hormone Biding Globulin (SHBG) and did a little poking around on the internet and found this useful site: SHBG - Clinical: Sex Hormone-Binding Globulin (SHBG), Serum

Lots of information but here's a synopsis of what I came away with. Some of the information I already knew, but some of it was new to me too. The thyroid-SHBG connection was of particular interest. I've always had high SHBG, but my labs do show that it has been higher since I started treatment with Armour Thyroid. I may need to reevaluate that part of my HRT protocol and do some dose-response testing in the future. The genetic variant of SHBG was also of particular interest. I've always theorized that the men in our family for generations have had excess SHBG, perhaps it's more of a genetic variant that binds sex hormones more aggressively.

1) SHBG binds sex steroids with high affinity (KD approximately 10[-10]M), dihydrotestosterone (DHT) ->testosterone (T) ->estrone/estradiol (E). Although each monomeric subunit contains 1 steroid binding site, the dimer tends to bind only a single sex-steroid molecule. The main function of SHBG is sex-steroid transport within the blood stream and to extravascular target tissues. SHBG also plays a key role in regulating bioavailable sex-steroid concentrations through competition of sex steroids for available binding sites and fluctuations in SHBG concentrations. Because of the higher affinity of SHBG for DHT and T, compared to E, SHBG also has profound effects on the balance between bioavailable androgens and estrogens. Increased SHBG levels may be associated with symptoms and signs of hypogonadism in men, while decreased levels can result in androgenization in women.

2) SHBG is synthesized in the liver. Metabolic clearance is biphasic, with a fast initial distribution from vascular compartment into extracellular space (half-life of a few hours), followed by a slower degradation phase (half-life of several days).

3) Excess thyroid hormones increase SHBG

4) Excess estrogens increase SHBG

5) There is an age-related gradual rise in SHBG production

6) Nutritional status affects SHBG production. Patients with anorexia nervosa have high SHBG levels.

7) Low SHBG levels may predict progressive insulin resistance, cardiovascular complications, and progression to type 2 diabetes.

8) There is a genetic variant of SHBG (Asp327->Asn) introduces an additional glycosylation site in 10% to 20% of the population, resulting in significantly slower degradation. These individuals tend to have higher SHBG levels for any given level of other factors influencing SHBG.

[kelkel]

Good stuff. Thanks YG55

[MuscleScience]

Awesome thanks!

[Quester]

-This seems to be leading to the point where you would like to test for that "SHBG (Asp327->Asn), " in your family?

[EDCG19]

Main reason shbg is low in people is usually them being overweight and having too much fat on them. The thing is there really is no way to raise your shbg levels are there?
Low shbg = higher conversion to estrogen

Something I haven't been able to figure out is low shbg actually bad long term and is there any way to change that? I have heard you can't raise shbg it finds its own level and stays there...

[hammerheart]

Main reason shbg is low in people is usually them being overweight and having too much fat on them. The thing is there really is no way to raise your shbg levels are there?
Low shbg = higher conversion to estrogen

Something I haven't been able to figure out is low shbg actually bad long term and is there any way to change that? I have heard you can't raise shbg it finds its own level and stays there...

Nope there is a correlation between low SHBG and metabolic syndrome but that doesn't imply causation.

Low SHBG itself is not a problem but for ppl on TRT it means sharper "peak and valleys" and thus increased conversion to E2.

SERMs like nolva or clomid are estrogen agonists in the liver, so they might help raising SHBG.