Early pregnancy human chorionic gonadotropin (hCG) isoforms measured by animmunometric assay for choriocarcinoma-like hCG

Human chorionic gonadotropin (hCG) exhibits molecular heterogeneity in both its protein and carbohydrate moieties. This communication describes change s in hCG isoforms detected directly in clinical samples. These isoforms, qu antified in blood or urine specimens, show a progression of change througho ut normal pregnancy. Early pregnancy produces a type of hCG that resembles, in terms of immunoreactivity, a major form of hCG excreted in choriocarcin oma. The isoforms predominate for the first 5-6 weeks of gestation and then diminish, being replaced with the hCG isoforms which predominate throughou t the remainder of pregnancy. The alteration in hCG isoform content occurs in both blood and urine. The progression of isoforms is best delineated by calculating the change in the ratio of the two forms, as many hCG assays ei ther do not detect or fail to discriminate among these isoforms. An analogo us pattern of hCG isoforms was observed in patients with in vitro fertiliza tion pregnancies. hCG isolated from the pituitary displayed binding charact eristics similar to those of the hCG derived from normal pregnancy urine. T he early pregnancy hCG isoforms appear to have a differential expression in normal pregnancy as opposed to pregnancies which will not carry to term, s uggesting that a determination of the relative balance of hCG isoforms may have diagnostic application in predicting pregnancy outcome.