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Home / Equine Research Bank / Animals (Basel) / Changes Associated with the Peri-Ovulatory Period, Age and P...
Animals : an open access journal from MDPI2021; 11(3); 891; doi: 10.3390/ani11030891

Changes Associated with the Peri-Ovulatory Period, Age and Pregnancy in ACTH, Cortisol, Glucose and Insulin Concentrations in Mares.

Abstract: Although there are many hormonal changes associated with reproduction, the effects of ovulation and early pregnancy on adrenocorticotropic hormone (ACTH) and insulin concentrations are poorly described. We hypothesise that both ovulation and early pregnancy will alter ACTH and insulin concentrations in healthy mares. Eighteen mares showing no clinical signs suggestive of, or laboratory findings consistent with, pituitary pars intermedia dysfunction PPID and insulin dysregulation (ID) are enrolled. ACTH, cortisol, insulin and glucose concentrations are measured over their peri-ovulatory period, as determined via ultrasounds and progesterone concentrations. The mares are grouped by age and gestation status, and a two-way repeated-measures ANOVA is used to determine the effects of age and early pregnancy, along with the peri-ovulatory period, on analyte concentrations. No significant effect of age, ovulation or early pregnancy is detected on the mares' cortisol, insulin or glucose concentrations; however, there is a significant effect of early pregnancy and ovulation on ACTH concentrations ( = 0.04 and = 0.04 respectively). ACTH concentrations change around ovulation and with early pregnancy. Therefore, knowledge of a mare's reproductive status might be beneficial when interpreting ACTH concentrations.
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Publication Date: 2021-03-20 PubMed ID: 33804751PubMed Central: PMC8003915DOI: 10.3390/ani11030891Google Scholar: Lookup
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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 conducted a thorough investigation of the impact of ovulation and early pregnancy on the concentrations of adrenocorticotropic hormone (ACTH) and insulin in mares. The results revealed that while ovulation and early pregnancy had a significant impact on ACTH levels, they had no discernible effect on cortisol, insulin, or glucose levels in horses.

Research Methodology

  • The study was conducted on a group of 18 mares or female horses. These mares did not display any clinical symptoms of pituitary pars intermedia dysfunction (PPID) or insulin dysregulation (ID), which could impact the data.
  • The scientists employed ultrasound examinations and monitored progesterone levels in the mares to pinpoint their peri-ovulatory period, i.e., the time around their ovulation.
  • Detailed measurements of the mares’ ACTH, cortisol, insulin, and glucose concentrations were taken during this period.
  • The horses were split into groups depending on their age and pregnancy status. These splits allowed the researchers to scrutinize possible effects of these categorizations on the distribution of these hormones and glucose.

Data Analysis and Findings

  • The researchers employed two-way repeated-measures ANOVA, a statistical method, to determine the influence of factors such as age, early pregnancy, and peri-ovulatory period on the levels of the hormones and glucose in the mares.
  • This analysis revealed a significant impact of both ovulation and early pregnancy on the levels of ACTH, with them changing around ovulation and with early pregnancy.
  • However, no significant effect of age or ovulation and early pregnancy was observed on the concentrations of cortisol, insulin, and glucose in the mares.

Conclusion and Implications

  • The finding that ACTH levels change around ovulation and early pregnancy has potential implications for how veterinarians interpret ACTH concentrations in mares. If a mare’s reproductive status is known, it may assist in making a more accurate assessment of ACTH levels.
  • This could, in turn, inform more nuanced and targeted treatment for mares suffering from hormonal imbalances or reproductive disorders.

Cite This Article

APA
Hicks GR, Fraser NS, Bertin FR. (2021). Changes Associated with the Peri-Ovulatory Period, Age and Pregnancy in ACTH, Cortisol, Glucose and Insulin Concentrations in Mares. Animals (Basel), 11(3), 891. https://doi.org/10.3390/ani11030891

Publication

Animals : an open access journal from MDPI
ISSN: 2076-2615
NlmUniqueID: 101635614
Country: Switzerland
Language: English
Volume: 11
Issue: 3
PII: 891

Researcher Affiliations

Hicks, Gemma R
  • School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia.
Fraser, Natalie S
  • School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia.
  • Samford Valley Veterinary Hospital, Samford, QLD 4520, Australia.
Bertin, François-René
  • School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia.

Grant Funding

  • N/A / John and Mary Kibble Trust

Conflict of Interest Statement

The authors declare no conflict of interest.

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Citations

This article has been cited 3 times.
  1. Hinrichsen SL, Yuen KY, Dryburgh EL, Bertin FR, Stewart AJ. Short-Term Effects of Temperature and Thyrotropin-Releasing Hormone Stimulation on Adrenocorticotropin Stability in Horses. Animals (Basel) 2022 Jan 28;12(3).
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  2. Kam YN, McKenzie K, Coyle M, Bertin FR. Repeatability of a thyrotropin-releasing hormone stimulation test for diagnosis of pituitary pars intermedia dysfunction in mature horses. J Vet Intern Med 2021 Nov;35(6):2885-2890.
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  3. Nowak AC, Macho-Maschler S, Biermann NM, Palme R, Dengler F. Investigating the interplay of stressors and health in horses through fecal cortisol metabolite analysis. Front Vet Sci 2025;12:1545577.
    doi: 10.3389/fvets.2025.1545577pubmed: 40264993google scholar: lookup
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