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Theriogenology2016; 86(1); 355-365; doi: 10.1016/j.theriogenology.2016.04.049

Review of the reproductive endocrinology of the pregnant and parturient mare.

Abstract: Analytical advancements, especially methods using gas or liquid chromatography tandem mass spectrometry, have allowed more specific and reliable measurement of multiple steroid hormones in the plasma of mares throughout gestation and the periparturient period. Data such as these will form the central focus of this review. The comprehensive analyses possible with liquid chromatography tandem mass spectrometry illuminate the key physiological and developmental transitions that make equine gestation unique. Weeks 6 to 20 encompass endometrial cup formation and equine chorionic gonadotropic secretion that stimulates primary corpora lutea and induces formation of secondary luteal structures. The period is defined by increased progesterone, 17OH-progesterone, and androstenedione secretion, providing substrate feeding the rise in estrone sulfate that can be used as an aid in the diagnosis of pregnancy. The 5α-reduced metabolite of progesterone, dihydroprogesterone (DHP), parallels progesterone secretion during this period at less than half the concentration. After week 12, progesterone declines, but DHP concentrations continue to increase, exceeding progesterone by week 16, thereby defining the luteo-placental shift in pregnane synthesis from ovarian to primarily placental thereafter. The growth of fetal gonads begins around week 14 and is defined by increasing dehydroepiandrosterone, among other androgens, which fuels placental estrogen secretion, functioning as a true fetoplacental unit. Metabolites of DHP (including allopregnanolone) dominate in late gestation, some exceeding DHP by 10-fold near term. However, all major pregnanes decrease from 3 days before foaling, when fetal cortisol is reportedly rising. Though unique, equine pregnancy and parturition share many features in common with those seen in human pregnancy and birth.
Copyright © 2016 Elsevier Inc. All rights reserved.
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Publication Date: 2016-04-21 PubMed ID: 27156685DOI: 10.1016/j.theriogenology.2016.04.049Google Scholar: Lookup
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  • Journal Article
  • Review

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article discusses advances in technology that have allowed for improved methods to measure several hormones in the blood of horses during pregnancy and the period around giving birth. These advancements shed light on the physiological changes and transitions that happen in equine gestation, contributing to our understanding of horse reproduction and how it relates to human reproduction.

Advancements in Analytical Methods

  • The research review highlights the significance of analytical advancements, particularly in the use of gas or liquid chromatography tandem mass spectrometry. These technologies have enabled more specific and reliable measurement of multiple steroid hormones in the plasma of pregnant horses.

Focus of The Review

  • The review’s central focus is data derived from these advanced analyses, which provide valuable insight into the physiological changes and developmental transitions occurring during equine gestation.

Study of Hormone Secretions During Pregnancy

  • Detailed hormonal changes are documented, specifying weeks in which significant hormonal shifts occur, the types of hormones involved, and their effect in the gestational process.
  • These changes include increased secretion of progesterone, 17OH-progesterone, and androstenedione, which especially occurs during weeks 6 to 20, along with the formation of endometrial cup and the secretion of equine chorionic gonadotropin.
  • It also describes the rise of estrone sulfate and its role as an aid to diagnose pregnancy.

Changes in Pregnane Synthesis and the Growth of Fetal Gonads

  • Detailed changes in the concentrations of hormones, progesterone, and dihydroprogesterone (DHP) are discussed. The shift in pregnane synthesis from ovarian to primarily placental after week 12 is underlined, along with the sustained growth of fetal gonads around week 14.
  • The rise of dehydroepiandrosterone and its contribution to fuel placental estrogen secretion are also discussed.

Comparison of Equine and Human Reproduction

  • Although horse pregnancy and parturition are unique, the paper notes that they share many features common with human pregnancy and birth.

Cite This Article

APA
Conley AJ. (2016). Review of the reproductive endocrinology of the pregnant and parturient mare. Theriogenology, 86(1), 355-365. https://doi.org/10.1016/j.theriogenology.2016.04.049

Publication

Theriogenology
ISSN: 1879-3231
NlmUniqueID: 0421510
Country: United States
Language: English
Volume: 86
Issue: 1
Pages: 355-365
PII: S0093-691X(16)30088-7

Researcher Affiliations

Conley, A J
  • Department of Population Health & Reproduction, School of Veterinary Medicine, University of California, Davis, California, USA. Electronic address: ajconley@ucdavis.edu.

MeSH Terms

  • Animals
  • Female
  • Horses / physiology
  • Parturition / physiology
  • Pregnancy
  • Pregnancy, Animal / physiology
  • Progesterone / blood
  • Progesterone / physiology

Citations

This article has been cited 23 times.
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