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Evidence That Termination of the Estradiol-Induced Luteinizing Hormone Surge in Women Is Regulated by Ovarian Factors

Departments of Obstetrics and Gynecology (K.D., I.M., P.V., A.K., I.E.M.) and Anesthesiology (G.S.), University of Thessalia, 41222 Larissa, Greece; and Clinical Chemistry Laboratory (C.K.), General Hospital of Athens "G. Gennimatas," 11527 Athens, Greece

Address all correspondence and requests for reprints to: Professor I. E. Messinis, Department of Obstetrics and Gynecology, University of Thessalia, 22 Papakiriazi Street, 41222 Larissa, Greece. E-mail: messinis{at}med.uth.gr.

Background: The endogenous LH surge is the result of the estrogen-positive feedback effect. However, the factors that are responsible for the termination of LH surge are not known.

Objective: The objective of the study was to investigate the mechanism that terminates the LH surge in women.

Subjects and Methods: Eight normally cycling women (aged 42–48 yr) were investigated in two cycles, i.e. cycle 1 (control) and cycle 2. In cycle 2 total abdominal hysterectomy plus bilateral salpingooophorectomy was performed on d 3. In both cycles, estradiol was administered transdermally at the dose of 100 µg on d 3 and 150 µg on d 4 and 5. Blood samples were obtained every 12 h from d 3 to 5 and every 6 h thereafter until d 9.

Results: In both cycles, after suppression of gonadotropins, the women displayed an endogenous LH surge. The time intervals between the commencement of estradiol treatment and the LH surge onset (73.5 ± 1.5 vs. 76.5 ± 2.5 h) and peak LH values (11.4 ± 1.9 vs. 12.4 ± 3.1 IU/liter) were comparable in the two cycles (mean ± SEM). After peaking, LH values decreased gradually in cycle 1, whereas in cycle 2 they remained stable and were higher than the corresponding values in cycle 1 (P < 0.05). Before the LH surge onset, estradiol values showed in both cycles a preovulatory pattern of changes, but starting 24 h after the onset of the LH surge, they were lower in cycle 2 (P < 0.05). Progesterone levels were similar in both cycles until the day of the LH surge onset, but in cycle 2 they declined thereafter and were lower than in cycle 1 (P < 0.05).

Conclusions: It is suggested that ovarian factors rather than exhaustion of pituitary reserves are important for termination of the endogenous LH surge during the normal menstrual cycle.

This article has been cited by other articles:

				I. E. Messinis Ovarian feedback, mechanism of action and possible clinical implications Hum. Reprod. Update, September 1, 2006; 12(5): 557 - 571. [Abstract] [Full Text] [PDF]