Radioimmunoassay of human follicle stimulating hormone: bias due to antisera.

ABSTRACT Anti-FSH serum has been produced in rabbits immunized with human pituitary FSH. This serum is utilized in a double antibody radioimmunoassay for measurement of FSH in small aliquots of human plasma and in preparations of purified gonadotropins. Two other antisera for FSH (courtesy of W. Odell and R. Midgley) were studied in parallel. None of the 3 antisera had significant cross-reaction with physiological levels of human growth hormone, luteinizing hormone, or chorionic gonadotropin. Each antiserum gave similar potency estimates for purified preparations of urinary gonadotropins dissolved in buffer and these agreed with the bioassay potency estimates. However, the values obtained in plasma samples by radioimmunoassay differed significantly, depending upon which of the 3 antisera was utilized for the assay. These different values cannot be attributed to variability of the trace protein, isotope, temperature, or time of incubation. It appears that some of the variation in FSH values reported from d...