Radioreceptor assay for human chorionic gonadotropin

A sensitive radioreceptor assay capable of detecting 100 pg of human chorionic gonadotropin has been developed using ovarian receptors and (125I)hCG. The dose-response curves of a series of urine and serum samples from pregnant women were linear and parallel to standard curves of 2nd International Standard hCG and purified hCG when logit of percent bound was plotted against log dose. Potency estimates of pregnancy sera, measured by radioreceptor assays, were approximately 2 times greater than those determined by radioimmunoassays. Examination of hCG concentrations in the urine of pregnant and nonpregnant women, using a receptor assay, showed good correlation with the result obtained with a standard agglutination pregnancy test. This readioreceptor assay, which can be made as sensitive as radioimmunoassay, provides a rapid and simple method for the measurement of biologically active hCG and LH.