Sex hormone binding globulin

Sex hormone binding globulin (SHBG) is a globular plasma protein whose function is to bind and transport testosterone, dihydrotestosterone, and oestradiol.

Measurement of SHBG is important because only the unbound fraction of sex hormones in the plasma is biologically active, and so when evaluating sex hormonal disorders one can only determine the biologically active fraction of sex hormones is one also knows the SHBG level.

The hepatic synthesis of SHBG increases when oestrogens and thyroid hormones increase, and the synthesis decreases when androgens and glucocorticoids increase.