Does the gonadotropin pulsatility of postmenopausal women represent the unrestrained hypothalamic—pituitary activity?
Authors: Rossmanith Winfried G , Handke-Vesely Annette , Wirth Ulrike , Scherbaum Werner A 
Published: December 2008

Rossmanith WG, Handke-Vesely A, Wirth U, Scherbaum WA. Does the gonadotropin pulsatility of postmenopausal women represent the unrestrained hypothalamic–pituitary activity? Eur J Endocrinol 1994;130:485–93. ISSN 0804-4643
Ovarian sex steroids profoundly modulate the gonadotropin pulsatile secretion in women. A gonadotropin pulsatility determined in the absence of any considerable ovarian sex steroid feedback, as in postmenopausal women (PMW), may thus represent the unrestrained activity of the hypothalamic-pituitary axis. We hypothesized that increases in the gonadotropin pulse frequencies and amplitudes during sex steroid replacements may be limited by those determined in the hypogonadal state of PMW. To address this assumption, we investigated the unstimulated the gonadotropin-releasing hormone (GnRH)-stimulated release of luteinizing hormone (LH) and folliclestimulating hormone (FSH) in PMW before and during sequential ovarian sex steroid treatments. Seven PMW (mean age 59.4 years) were studied initially during unreplaced conditions (control studies), then on the last day of a 21-day course of oral estradiol valeriate (F2) administrations (2 mg daily) and, finally, on the last day of a 21-day course of oral estradiol–progesterone (E2/P4) replacements (2 mg of E2 and 200 mg of micronized P4 daily). On all study occasions, blood was drawn at 10-min intervals for 10 h and GnRH (25 μg iv) was administered 8 h after initiation of blood collections. Compared to control conditions, the basal serum estrogen (estrone and E2) and progesterone (P4) concentrations markedly increased (p< 0.001) following oral E2 or E2/P4 treatments. As determined by Cluster pulse algorithm, LH and FSH were found to be released episodically during each study condition. Mean LH and FSH release rates declined (P< 0.05 or less) during E2 and E2/P4 regimens. Compared to control studies, the LH and FSH pulse frequencies and interpulse intervals remained virtually unchanged during E2 replacements. Yet, a slowing (p <0.05) of the LH but not of the FSH interpulse interval was evident during E2/P4 replacements. While the LH pulse amplitudes tended to increase during E2 and E2/P4 treatments, a decrease (p <0.05) was noted for the FSH pulse amplitudes during either replacement regimen. Although the absolute GnRH-stimulated LH and FSH increments were highest (p <0.05 or less) in the hypogonadal state, the percentage GnRH-mediated gonadotropin increments did not differ between the study conditions. Results of the current study demonstrate that ovarian sex steroid replaceent to PMW can influence markedly both the unstimulated and GnRH-stimulated gonadotropin secretion. Yet, the changes in the LH and FSH pulse frequencies and amplitudes during sex steroid replacements are confined to those determined in the hypogonadal state of PMW. Thus, we infer that the gonadotropin pulsatility of PMW may reflect the unrestrained activity of the hypothalamic–pituitary axis.
Winfried G Rossmanith, Department of Obstetrics-Gynecology, University of Ulm, Prittwitzstrasse 43, D-89075 Ulm, Germany