SHBG

SHBG (sex hormone-binding globulin) encodes a glycoprotein secreted mainly by the liver into the bloodstream, where it binds testosterone and estradiol with high affinity and thereby controls how much of these sex hormones circulates in free, biologically active form versus bound and inactive form. Common SHBG variants shift baseline circulating SHBG concentration, which in turn affects free sex-hormone availability; the lead variant at the locus is rs12150660, which tracks a promoter repeat controlling how much SHBG the liver transcribes, while the coding variant rs6259 is a smaller independent signal acting through slower clearance of the protein.