Pituitary response to exogenous LHRH in superovulated women

Abstract

The response of the pituitary to exogenous LHRH was investigated in 9 normally ovulating women during the late follicular phase of a spontaneous (control) cycle, a cycle during treatment with clomiphene and a cycle during treatment with 'pure' FSH. During clomiphene treatment, basal FSH concentrations increased significantly up to Day 6 of the cycle and then decreased progressively while basal LH values showed a continuous rise. During treatment with FSH, basal LH concentrations decreased significantly. The response of both FSH and LH to LHRH showed a significant and quantitatively similar decrease during clomiphene or FSH administration as compared to the spontaneous cycles. It is suggested that basal secretion of FSH and LH is regulated by two separate mechanisms, and that an ovarian inhibitory factor(s) attenuates the response of both FSH and LH to exogenous LHRH and possibly the endogenous LH surge in superovulated cycles.

Inhibition of LHRH-induced LH and FSH release by gonadotrophin surge-attenuating factor (GnSAF) from human follicular fluid

“…GnSAF is a putative ovarian factor which in superovulated women attenuates the pituitary response to exogenous LHRH (Messinis & Templeton, 1989, 1990. In the present study an attempt was made to determine whether hFF obtained from superovulated women contains GnSAF bioactivity.…”

“…The degree of LH surge attenuation is related to the degree of ovarian hyperstimulation and it has been suggested that ovarian non-steroidal factors are responsible (Messinis et ai, 1986b; Messinis & Templeton, 1987). The pituitary response to exogenous LHRH is signifi¬ cantly attenuated, in the mid-and late follicular phases ofthe cycle, in women hyperstimulated with clomiphene citrate or 'pure' FSH (Messinis & Templeton, 1989, 1990. These studies have provided evidence that hyperstimulated ovaries produce a substance which attenuates the endogenous LH surge through the reduction of the pituitary response to LHRH.…”

“…These studies have provided evidence that hyperstimulated ovaries produce a substance which attenuates the endogenous LH surge through the reduction of the pituitary response to LHRH. This factor has been termed gonadotrophin surge-attenuating factor (GnSAF: Messinis & Templeton, 1989, 1990.…”

Attenuin: What It Is, How It Works and What It Does

“…Over recent decades, the search for putative new substances secreted by the ovaries has provided new insights into the role of the ovaries in gonadotropin secretion. This chapter focuses on the factor known as attenuin (Messinis & Templeton, 1989;Sopelak & Hodgen, 1984).…”

Ο ωοθηκικός έλεγχος της υποφυσιακής ευαισθησίας στη GnRH στις γυναίκες με PCOS

“…Υπάρχουν συσσωρευµένες αποδείξεις ότι ένας µη στεροειδικός ωοθηκικός παράγων, που ονοµάζεται GnSAF, πιθανόν να εµπλέκεται στον έλεγχο της υποφυσιακής ευαισθησίας στη GnRH στις φυσιολογικές γυναίκες, ανταγωνιζόµενος την ευαισθητοποιό επίδραση της Ε2 (Messinis and Templeton, 1989;Fowler et al, 2003;Messinis, 2006). Πρόσφατα δεδοµένα παρέχουν ενδιαφέρουσες πληροφορίες όσον αφορά το χαρακτηρισµό αυτού του παράγοντα (Karligiotou et al, 2006).…”