The Functional Relationship between Priming and Releasing Actions of Luteinizing Hormone-Releasing Hormone*

Abstract

To examine the relationship between the priming and releasing actions of LRF on LH secretion, 14 normal cycling women received 4 different rates of LRF infusion (0.005, 0.01, 0.05, and 0.1 microgram/m2.min for 4 h). The releasing action of the infusion was measured as the area under the curve and the priming effect was assessed by the acute LH increment in response to a test pulse of LRF (10 microgram) at the end of infusion. At the lower 2 infusion rates, there were only minor changes in releasing function, but it increased exponentially (r = 0.986) with higher rates of infusion. In contrast, the priming effect of the lower 2 doses of infusion increased markedly as a function of infusion rate, but no additional priming was found with the higher rates of infusion. Thus, over the range of infusion rates employed, the releasing and priming functions of LRF appear to be dose dependent. These results indicate that the interdependent releasing and priming actions of LRF on LH secretion are functionally dissociable and that large elevations of LRF tend to favor release, while small LRF increments seem to promote priming preferentially.

Effects of Oestradiol on Plasma Concentrations of Luteinizing Hormone in Ovariectomized Ewes with Clover Disease

“…For example, the higher levels of LH in entire affected ewes result at least partly from more frequent LH peaks (Rodgers et al 1980), indicating that the release of gonadotrophin-releasing hormone (GnRH) is more frequent in these ewes (Clark and Cummins 1982). If the small releases of GnRH seen by Clark and Cummins (l982) also occur more frequently in affected ewes, these may prime the pituitary to respond, as has been reported in women treated with GnRH (Hoff et al 1979). An increased responsiveness of the pituitary is also indicated by the more rapid surge of LH reported in entire affected ewes by Chamley et al (1981).…”

Prolactin-Releasing Action of a Low Dose of Exogenous Gonadotropin-Releasing Hormone Throughout the Human Menstrual Cycle

“…At 9.00 a.m. a low dose (10 ug) of GnRH was intravenously injected. The above dose was selected because gonadotropin release after its administration is regarded as a marker o f pituitary responsiveness to GnRH [13,27). In addition, the dose o f 10 ug o f GnRH is be lieved to induce physiological blood concentrations, so that it is often selected for ovulation induction with pulsatile GnRH admin istration [for review see 16], Blood samples were obtained every 15 min both before ( -30, -15, 0 min) and for 2 h after GnRH injec tion.…”

Diagnostic Utility of a Low-Dose Gonadotropin-Releasing Hormone Test in the Context of Puberty Disorders

“…A dose of 10 µg elicits LH and FSH increments of approximately 33 and 40%, respectively, of the maximal response to the 250-µg dose [23]and has been used to study gonadotroph responsiveness, as opposed to maximal secretory capacity, in adult men [15, 16, 17]. Even smaller doses of approximately 1 µg GnRH are sufficient to produce LH secretory bursts similar in magnitude to spontaneous LH pulses in adult men [20].…”

“…The most widely used dose is 100 µg or 100 µg/m 2 which assesses maximum secretory capacity of the pituitary gonadotrophs [1, 10, 12]. However, a much smaller dose of 10 µg has been used in several studies in adults to distinguish subtle differences in pituitary responsiveness to GnRH [15, 16, 17]. In children, early puberty is heralded by nocturnal pulsatile GnRH secretion resulting in a gradual augmentation of nocturnal pulsatile LH release, both through direct stimulation of the gonadotrophs and through a priming or sensitizing action [12, 13, 18, 19].…”