HLH beta core fragment immunoreactivity in the urine of ovulating women: a sensitive and specific immunometric assay for its detection.

Recently, we isolated an hLH beta core fragment (hLHβcf) from human pituitaries. This molecule is homologous to the hCG beta core fragment (hCGβcf), which may be a marker of normal pregnancy, Down syndrome, and certain cancers. We now report antibodies to the hLHβcf, four of which have been applied in sensitive immunoradiometric assays for urinary measurements. One of the antibodies recognizes an epitope on the hLHβcf, which is not present on the hCGβcf, hLH, or hLHβ. This specific hLHβcf antibody acts cooperatively with other newly-developed antibodies reported here to produce an assay with a sensitivity of 1 fmol/ml of hLHβcf. The specificity of these new IRMA systems will make it possible to measure the hLHβcf in urine in the presence of hLH, hLH beta, or the hCGβcf. Although the hLHβcf used to develop specific antibodies was purified from pituitaries, the assays developed recognize this metabolite in urine. Measurements of heterodimeric hLH as compared to hLHβcf in the urine of cycling women indicated that the concentration of hLHβcf rose as high as 6-7 times the concentration of hLH starting a day after the midcycle surge. The new measuring systems allow the precise quantitation of this hLH metabolite in urine.