Plasma luteinizing hormone-releasing hormone levels in normal women and patients with amenorrhea.

Plasma levels of immunoreactive luteinizing hormone-releasing hormone (LH-RH) in 89 women with normal menstrual cycles and 109 patients with amenorrhea of various etiologies were determined by specific radioimmunoassay after methanol extraction. The LH-RH levels in patients with hypergonadotropism and Sheehan's syndrome were more than 10 pg/ml, and were significantly higher than basal levels during normal cycles (4.2 +/- 0.3 pg/ml). The mean levels of LH-RH were low in all hypogonadotropic patients with amenorrhea, with the exception of a few patients who showed high LH-RH levels suggestive of a pituitary lesion. The LH-RH levels in patients with polycystic ovary syndrome were comparable with basal levels during normal cycles. It is concluded that, although there is considerable overlap of the plasma LH-RH levels in each group of amenorrheic patients divided according to gonadotropin level, determination of LH-RH levels may be useful for the differentiation of hypothalamic amenorrhea from pituitary amenorrhea.