Effects of the (imBzl)D-His6, Des-Gly analog of GnRH on gonadotropin and estradiol secretion in normal women.

The acute gonadotropin and estradiol responses following single subcutaneous injections of 10, 50, 100 and 200 micrograms of [(imBzl)]D-His6,Pro9-NEt]-GnRH were compared to those after 100 micrograms of [D-Trp6, Pro9-NEt]-GnRH. The gonadotropin responses after 50-100 micrograms of the D-His analog of GnRH were equivalent to those following 100 micrograms of the D-Trp analog. The ovarian E2 response, a reflection of the total cumulative secretion of gonadotropins, was similar at 100 micrograms of each analog. The estradiol response paralleled the increasing gonadotropin response accompanying the graded doses of the D-His analog, indicating the lack of a direct inhibitory action of this GnRH agonist on the ovary. Assessment of both gonadotropin and estradiol responses appears to be satisfactory for assessing relative potency among GnRH agonistic analogs.