LH and FSH responses to synthetic LH-RH in various estradiol levels of anovulatory women (author's transl)

Abstract

Synthetic LH releasing hormone (LH-RH) is effective in increasing both serum LH and FSH in humans. Therefore, LH-RH is used to clarify the function of the hypothalamic pituitary ovarian axis in adult women. Variations in response to synthetic LH-RH during different phases of the menstrual cycle are known. These variations may be due to changes in the ovarian secretion of sex streoid hormones during the menstrual cycle. In the present study, effects of serum estradiol (Ed) on pituitary gonadotropin response to synthetic LH-RH were studied in 55 subjects without ovulation. Serum levels of LH, FSH and Ed were determined before and at 30 min after intramuscular administration of 100 mug LH-RH. LH and FSH levels in the serum were measured by the double antibody method of radioimmunoassay. Ed levels were determined by the radioimmunoassay method of T. Makino, using the antiserum against Ed-6-oxime-BSA donated by Dr. T. Makino and applied to the microcolumn of sephadex LH 20. Preliminary evidence about Ed levels during the normal menstrual cycle and in anovulatory women suggested that an Ed level under 30 pg/ml indicates the presence of a small amount of Ed. Therefore, 55 patients were divided into 2 groups; the low Ed group that showed low basal Ed levels (under 30 pg/ml) and the Ed normal group that showed normal basal Ed levels (over 30 pg/ml). Pituitary gonadotropin responses to synthetic LH-RH were studied in these two groups. No statistical difference was shown between the two groups studied for basal LH level and FSH level. After LH-RH injection in the Ed normal group, serum LH level was significantly higher and serum FSH level was significantly lower than that in the low Ed group. Then, in order to clarify the difference in two groups, the ratio of LH to FSH (LH/FSH) before and after administration of LH-RH was examined. The ratio in the Ed normal group was significantly higher than one in the low Ed group before and after administration of LH-RH. Moreover, the percentage increase of the ratio was significantly larger in the Ed normal group than that in the low Ed group. A positive correlation (r=0.4228, p less than 0.01) was found between LH/FSH following administration of LH-RH and circulating the Ed level. These results suggest that the response of pituitary gonadotropins to LH-RH is changed by serum Ed and that serum Ed causes a differential release of LH and FSH in response to LH-RH. The data seem to demonstrate that LH-RH and serum Ed show a complex interplay in releasing LH and FSH.