Human chorionic gonadotropin Molecular forms, detection, and clinical implications

Different molecular forms of human chorionic gonadotropin (hCG) have been identified in biologic fluids of patients with various physiopathologic processes. These materials include (a) the intact heterodimer hCG comprising two mature a and beta subunits, and (b) the uncombined or free forms of the a (hCGalpha) and beta subunit (hCGbeta), and several fragments o f hCG such as the nicked forms o f both hCG and free hCGbeta and its ending degradation product, the beta-core fragment or hCGbetacf The determination of hCG and related molecules in biologic fluids is usually achieved by immunologic procedures, but discrepancies among kits remain a problem in clinical practice. Specific measurements of hCG and of, independently, its free beta subunit are important in the diagnosis and follow-up of either trophoblastic diseases or testicular cancers, whereas only the free hCGbeta has to be assayed for detection in nongonadal and nonplacental tumors.