Is GnRH reduced at the midcycle surge in the human? Evidence from a GnRH-deficient model

Neuroendocrinology
K A MartinJ E Hall

Abstract

Recent studies indicate that the midcycle gonadotropin surge in the human occurs without an increase in hypothalamic gonadotropin-releasing hormone (GnRH) pulse frequency. In addition, previous studies employing a GnRH antagonist to provide a semiquantitative estimate of endogenous GnRH secretion suggest that the overall amount of GnRH secreted is decreased at the time of the surge. To investigate the hypothesis that a normal gonadotropin surge can be generated in the human with a decreased amount of GnRH at the midcycle, 7 GnRH-deficient subjects underwent two cycles of a physiologic regimen of intravenous pulsatile GnRH therapy. In the control cycle, 75 ng/kg/bolus of GnRH, a dose known to be sufficient for folliculogenesis, was administered throughout the cycle, using physiological frequencies. In a second cycle, the bolus dose of GnRH was decreased by one-half log order to 25 ng/kg just prior to the luteinizing hormone surge and returned to 75 ng/kg after documented ovulation. All cycles were ovulatory. The peak luteinizing hormone level (77.4 +/- 9.7 vs. 67.5 +/- 17.6 IU/l) did not differ between the control and decreased GnRH cycles. There was no difference in the peak serum estradiol level (475.8 +/- 144.1 vs. 493.2 +/- ...Continue Reading

Citations

Sep 27, 2001·Endocrinology and Metabolism Clinics of North America·J E Hall, S Gill
Jul 20, 2011·Toxicological Sciences : an Official Journal of the Society of Toxicology·James W SimpkinsCharles B Breckenridge
May 12, 2011·American Journal of Physiology. Endocrinology and Metabolism·N D ShawJ E Hall
Oct 19, 2010·Brain Research·Kei-Ichiro MaedaHiroaki Okamura

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