Measurement of receptor-bound unlabelled physiologically active lutropin (luteinizing hormone, LH) was possible by a modified radioimmunoassay. The conventional radioimmunoassay conducted at 4° C was inadequate, whereas the modified assay performed at 37° C could measure receptor-bound lutropin. The radioimmunoassay at 37° C takes only 36h for completion compared with 5-7 days at 4° C. The sensitivity and range of dose-response curves are, however, unaltered. The validity of the technique was established by a number of criteria.
