More info about SHBG and now Zinc.

[Guest guest]

I feel the men on T3 only meds for RT3 need to keep an eye on there SHBG levels.

http://tinyurl.com/36nxzdq

Structure/function analyses of human sex hormone-binding globulin: effects of

zinc on steroid-binding specificity

In humans, sex hormone-binding globulin (SHBG) binds and transports the

biologically most important androgens and estrogens in the blood, and regulates

the access of these steroids to their targets tissues. In addition to binding

sex steroids, SHBG has specific binding sites for divalent cations including

calcium and zinc. Zinc binding to a site at the entrance of the steroid-binding

pocket in human SHBG has been shown to reduce its affinity for estrogens, while

having no impact on the binding of C19 steroids. Crystallographic studies

indicate that C18 and C19 steroids are bound in opposite orientations within the

SHBG steroid-binding site, and we have obtained new information that supports a

molecular model explaining the mechanism by which zinc alters the affinity of

human SHBG for estrogens, by studying directly the estradiol-binding properties

SHBG variants created by site-directed mutagenesis. In this model, the

coordination of a zinc ion by the side chains of residues Asp65 and His136

eliminates a critical hydrogen bond between Asp65 and the hydroxyl at C3 of

estrogens, such as estradiol and 2-methoxyestradiol, and causes disorder in a

polypeptide loop segment that covers the steroid-binding site. The combination

of these structural changes explains the specific decrease in the affinity of

human SHBG for C18 steroids in the presence of a zinc ion.