CHARACTERISTICS OF URINARY LUTEINIZING-HORMONE (LH) DURING THE INDUCTION OF LH SURGES OF DIFFERENT MAGNITUDE IN BLOOD

Urinary luteinizing hormone (LH) testing has been proposed as a reliab le method for the prediction of ovulation but its accuracy has been ch allenged by some studies. To check how accurately the oscillations of urinary LH reflected the plasma changes, surges of LH of different mag nitude and duration were artificially induced in plasma and the hormon e was measured simultaneously in urine. Post-menopausal women (n = 16) were stimulated during 1 week with a combination of transdermal oestr adiol (400 mu g) and i.m. progesterone (25 mg on day 4, 50 mg on day 5 ) to obtain an LH discharge comparable with the pre-ovulatory LH peak. A short and moderate peak of LH was induced by the i.v. injection of 100 mu g gonadotrophin-releasing hormone (GnRH) in six premenopausal w omen, whereas an LH discharge of higher amplitude and longer duration was induced by a single dose of 0.3 mg s.c. buserelin. The total urine production of the day was fractionated into 8 h periods. LH was measu red by a commercial radioimmunoassay. Unambiguous peaks of LH were det ected in the urine of all the women stimulated with either oestradiol plus progesterone or buserelin, but in only three out of the six women receiving GnRH. The urine LH reproduced the plasma changes of the hor mone with short delay since the peaks were mostly detected in the same time fraction in which the serum discharge occurred.