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Gonadotropin-Estradiol Responses to a Superactive Luteinizing Hormone-Releasing Hormone Agonist in Women^*

ROBERT F. CASPER, KATHARINE L. SHEEHAN and SAMUEL S. C. YEN

Department of Reproductive Medicine, School of Medicine (T-002), University of California, San Diego, La Jolla, California 92093

ABSTRACT. After the sc administration of 1, 10, and 50 µg of the LRF agonist [D-Trp⁶,Pro,⁹,NEt]LRF, dose-dependent increments in circulating levels of LH, FSH, and estradiol were observed which were 2- to 3-fold greater in the late than in the early follicular phase. The 10-µg dose of LRF agonist appears to induce a maximal acute gonadotropin-estradiol response. Both 10- and 50-µdoses of the agonist elicited gonadotropin increments which were several times greater than that seen during the midcycle surge. The only difference between the two doses was the more sustained action on gonadotropin release of the latter. It is estimated that this superactive LRF agonist is approximately 140 times more potent than the decapeptide LRF. These observations provide information useful in the application of this LRF agonist for clinical studies. (J Clin Endocrinol Metab 50: 179, 1980)

^* This work was supported by NIH Grant HD-12303 and Rockefeller Foundation Grant RF-75029.

Research Fellow in Reproductive Endocrinology, supported by the Medical Research Council of Canada.

Research Fellow in Reproductive Endocrinology.

To whom all correspondence and requests for reprints should be addressed.

Received April 12, 1979.