Step I SHBG increase lowers free testosterone = gynecomastia?

[peroxidase]

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It doesnt make sense to me though because when TBG increases in pregnancy/OCP use then total T4 increases and free T4 stays the same.

If you have an increased SHBG, why is the free testosterone getting lowered?

I saw there was another SHBG thread but this was not tackled in it.

Godspeed.

 

[Girfaroo]

SHGB binds testosterone, so there is less free (unbound testosterone). The unbound/free testosterone is what's active.

I think there's a combination of less free testosterone and increased estrogen (conversion from testosterone) that leads to the gynecomastia. Someone please correct me if I'm wrong.

 

[peroxidase]

SHGB binds testosterone, so there is less free (unbound testosterone). The unbound/free testosterone is what's active.

I think there's a combination of less free testosterone and increased estrogen (conversion from testosterone) that leads to the gynecomastia. Someone please correct me if I'm wrong.

yes well i understand that
but why isnt it the same mechanism as what is happening with TBG

 

[HelpPleaseMD]

That is a good question peroxidase. I thought about it too when I was doing the questions but gave up when I could not think of a concrete answer. Maybe the thyroid hormones are more sensitive via feedback loop cause they are much more vital than the sex hormones to survival. But yea... no idea

 

[frankyazz]

SHBG has a higher affinity for testosterone compared to estrogens.

 

[lemonade90]

Back in our endo block I asked our professor the same question re why sex hormones aren't similar to thyroid hormones in terms of protein binding...she just told me that they were less tightly regulated compared to thyroid hormones. Although there is probably a deeper philosophical reason which various research papers wax and wane about, that is good enough for me.