Rapid oscillation of circulating gonadotropins in postmenopausal women.

The circulating levels of of radioimmunoassayable LH and FSH in three postmenopausal women were measured in samples drawn at one minute intervals for a period of 150 or 300 min in order to ascertain the existance of short term oscillation on the plasma content of pituitary gonadotropins. Radioimmunoassay methods and sampling procedures fulfilled all the requirements of quality control. Rapid and non-coincident oscillation in the plasma levels of both LH and FSH at the interval studied were observed in all cases. Statistical analysis disclosed that in addition to short-term gonadotropin fluctuation, the data successfully fit in a 120 min periodic function and the graph resembled a sine wave that was also compatible with an ultradian oscillatory pattern.