Detection of ovulation by a radioreceptor assay for human luteinizing hormone

A specific, sensitive, and rapid radioreceptor assay (RRA), employing membranes from bovine testes as receptor and [125I]hLH as radioligand, has been developed for measurement of human LH in serum. This RRA was used to determine the time of ovulation in seven women. For comparison, four hourly values around midcycle were measured by RIA. The sensitivity of the RRA was 0.78 ng/ml serum and could be increased by prolonged incubation. The coefficient of within and between assay variation at the 50% inhibition level was 7% and 13%, respectively. The mean index of discrimination (RRA/RIA) was 1.02, expressed by the slope of the regression curve. The coefficient of correlation was 0.97. In all women, the LH surge was detected by RRA, and the subsequent ovulation was verified within 30 h by endoscopic examination of the ovaries, as well as serum progesterone concentrations of more than 5 ng/ml on the fifth day after ovulation. As shown, prospective ovulation timing can be done by this simple and accurate method. The RRA can be useful in infertility therapy such as artificial insemination.