The Functions of Corticosteroid-Binding Globulin and Sex Hormone-Binding Globulin: Recent Advances*

The presence of corticosteroid-binding globulin (CBG) in plasma was detected about 30 yr ago, and of sex hormone-binding globulin (SHBG) about 20 yr ago. In the interval since their discovery, sophisticated binding and RIAs have been devised for their measurement; their concentrations in plasma and other biological fluids, from milk to saliva, have been measured in myriad clinical conditions in humans, and numerous experimental ones in animals; their phyletic distribution has been examined; they have been isolated and their complementary DNAs (cDNAs) cloned; their binding specificities for steroids have been examined in heroic detail; hormonal and drug influences on their plasma concentration in vivo, and their secretion by liver cells in vitro, have been widely explored; they have been the subject of two long, splendid monographs (1, 2) and many shorter reviews (3–11) wherein the original citations for the first part of this sentence may be found—and yet we still have not come to a consensus on what it is that they do. Undeniably, they bind certain steroids. But to what biological end?