Recent advances in the chemistry and immunochemistry of human chorionic gonadotropin: impact on clinical measurements.

SINCE the discovery of human chorionic gonadotropin (hCG) by Hirose (1) and Ascheim and Zondek (2) nearly three quarters of a century ago, its measurement has been the basis of pregnancy diagnosis and, coincidentally, a marker for many trophoblastic and nontrophoblastic tumors, including some tumors of the testes (3). The first measurements of hCG were by biological activity, which restricted detection to the intact, heterodimeric molecule. The advent of immunoassays in the 1960s (4) permitted not only quantification of the parent molecule but also differential estimation of gonadotropin free subunits and fragments. Since then the isolation and characterization of an ever expanding spectrum of hCG-related molecular forms in blood and urine have begun to enlarge the scope of clinical applications served by their measurement. Variations in the hCG molecule isolated from biological fluids include the following: those affecting sialic acid content (5–7) or carbohydrate structure and composition (8–11), those ...