title: Progesterone acutely increases LH pulse amplitude but does not acutely influence nocturnal LH pulse frequency slowing during the late follicular phase in women.
abstract: Progesterone (P) is the primary effector of LH (and by inference gonadotropin-releasing hormone) pulse frequency slowing in cycling women, but the time course of this action is unclear. We hypothesized that P administration to estradiol (E2)-pretreated women would slow LH pulse frequency within 12 h. We studied eight normally cycling women in two separate cycles (follicular phase, cycle days 7-11). After 3 days of E2 pretreatment (0.2 mg/day via transdermal patches), a 25-h blood sampling protocol (starting at 0800) was performed to define LH pulsatility. Oral micronized P (100 mg) or placebo (PBO) was administered at 1800 in a randomized, double-blind fashion, with treatment crossover occurring during a subsequent cycle. The 10-h mean P concentration increased from 0.6+/-0.1 ng/ml before P (0800-1800) to 3.9+/-0.3 ng/ml after P administration (2200-0800, P<0.01). Ten-hour mean LH interpulse interval increased significantly after both P and PBO administration, with no significant difference between P and PBO. In contrast, mean LH, LH amplitude, and mean FSH increased significantly within 4 h of P administration, but not after PBO. We conclude that, in E2-pretreated women in the late follicular phase, 1) nocturnal LH pulse frequency is not acutely (within 12 h) influenced by P administration; 2) an acute increase in P causes pronounced augmentation of gonadotropin pulse amplitude within 4 h; and 3) LH pulse frequency slows overnight during the second half of the follicular phase.
authors.affiliation: Center for Research in Reproduction, Box 800391, Department of Internal Medicine, University of Virginia Health System, Charlottesville, VA 22908, USA. cm2hq@virginia.edu
authors.forename: Christopher R
authors.initials: CR
authors.lastname: McCartney
authors.forename: Susan K
authors.initials: SK
authors.lastname: Blank
authors.forename: John C
authors.initials: JC
authors.lastname: Marshall
mesh_terms: D000284:Administration, Oral; D000328:Adult; D002940:Circadian Rhythm / Q000187:drug effects*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D005498:Follicular Phase / Q000097:blood / Q000187:drug effects*; D012739:Gonadal Steroid Hormones / Q000097:blood; D006801:Humans; D007986:Luteinizing Hormone / Q000378:metabolism*; D010919:Placebos; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*; D011673:Pulsatile Flow / Q000187:drug effects
chemical_list: D012739:Gonadal Steroid Hormones; D010919:Placebos; D011374:Progesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone