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Ovarian Cycle01:27

Ovarian Cycle

The menstrual cycle includes a critical component known as the ovarian cycle, which undergoes two main phases each month—the follicular phase and the luteal phase. The follicular phase is variable and averaging around 14 days. Ovulation, triggered by a surge in luteinizing hormone (LH), marks the transition between the two phases. The second phase, the luteal phase, is relatively consistent, lasting approximately 14 days, and is marked by the activity of the corpus luteum. While a cycle length...
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Analysis of Chromosome Segregation, Histone Acetylation, and Spindle Morphology in Horse Oocytes
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Published on: May 11, 2017

Treatment with human chorionic gonadotropin (hCG) for ovulation induction is associated with an immediate

O J Ginther1, M A Beg, E L Gastal

  • 1Eutheria Foundation, Cross Plains, WI 53528, USA. ginther@svm.vetmed.wisc.edu

Animal Reproduction Science
|October 7, 2008
PubMed
Summary

Human chorionic gonadotropin (hCG) treatment in mares triggers ovulation and influences hormone levels. While hCG affects estradiol and luteinizing hormone (LH) concentrations, the natural LH surge and estradiol decrease around ovulation remain consistent compared to controls.

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Area of Science:

  • Veterinary Medicine
  • Reproductive Endocrinology
  • Equine Science

Background:

  • Understanding hormonal regulation of ovulation is crucial for equine reproduction.
  • Human chorionic gonadotropin (hCG) is commonly used to induce ovulation in mares.
  • The precise effects of hCG on endogenous estradiol and luteinizing hormone (LH) require further elucidation.

Purpose of the Study:

  • To investigate the impact of an ovulation-inducing dose of hCG on estradiol and LH concentrations in mares.
  • To compare hormonal profiles between hCG-treated mares and control groups.

Main Methods:

  • Experiment 1: Assessed ovulation time, LH surge timing, and estradiol decline in hCG-treated versus control mares.
  • Experiment 2: Monitored hCG, estradiol, and LH concentrations over 48 hours post-hCG administration.
  • Hormone levels were quantified using established assays.

Main Results:

  • hCG treatment reliably induced ovulation within approximately 48 hours.
  • Estradiol levels significantly decreased within 6 hours after hCG administration (P<0.003).
  • LH exhibited a significantly greater rate of increase after 12 hours post-hCG (P<0.02).
  • The endogenous LH surge and estradiol decrease, when synchronized with ovulation, were comparable between hCG-treated and control groups.

Conclusions:

  • hCG administration in mares stimulates a decrease in estradiol, followed by an accelerated increase in LH.
  • Despite exogenous hCG influencing hormone dynamics, the natural LH surge and estradiol decline relative to ovulation are not significantly altered compared to untreated mares.