Journal of veterinary internal medicine2016; 30(2); 653-663; doi: 10.1111/jvim.13839

Effect of Age, Season, Body Condition, and Endocrine Status on Serum Free Cortisol Fraction and Insulin Concentration in Horses.

Abstract: Increased free cortisol fraction is associated with insulin dysregulation (ID) in people with Metabolic Syndrome and Cushing's Disease. Free cortisol has not been investigated in equine endocrine disorders. Objective: (1) In healthy horses, sex, age, body condition score (BCS), and season impact free cortisol; (2) free cortisol is increased in horses with Pituitary Pars Intermedia Dysfunction (PPID) or Equine Metabolic Syndrome (EMS). Methods: Fifty-seven healthy horses; 40 horses and ponies with PPID (n = 20) or EMS (n = 20). Methods: Prospective study. Serum collected seasonally from healthy animals and archived serum from PPID and EMS animals was analyzed for insulin, total and free cortisol concentrations, and free cortisol fraction (FCF). Linear mixed models were used to determine effects of age, sex, season, and BCS on hormones in controls. Hormone measurements were compared between disease groups and age- and season-matched controls with t-tests. EMS and hyperinsulinemic PPID animals were combined in an ID (hyperinsulinemia) group. Results: Free cortisol concentrations were increased in overweight/obese controls (0.3 ± 0.1 μg/dL) compared to lean controls (0.2 ± 0.1 μg/dL; P = .017). Mean FCF was significantly higher in animals with PPID (8.8 ± 5.8 μg/dL, P = .005) or ID (8.8 ± 10.2 μg/dL, P = .039) than controls (5.0 ± 0.9 μg/dL), but total cortisol concentrations were similar (P ≥ .350) (PPID: 4.2 ± 4.3 μg/dL; ID: 5.0 ± 4.5 μg/dL; controls: 4.6 ± 1.7 and 5.1 ± 2.1 μg/dL). Conclusions: Increased FCF is associated with obesity in healthy horses and with ID (hyperinsulinemia) in horses and ponies with endocrine disease. Decreased plasma cortisol-binding capacity could be a component of these endocrine disorders in horses.
Publication Date: 2016-02-09 PubMed ID: 26860336PubMed Central: PMC4913614DOI: 10.1111/jvim.13839Google 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.

This research study investigates the factors affecting the concentration of free cortisol, a stress hormone, and its relationship with insulin dysregulation in horses, finding that increased free cortisol is associated with obesity in healthy horses and metabolic or pituitary gland disorders in ill horses.

Objectives and Methods

  • The main objectives of the study were to investigate the impact of sex, age, body condition, and season on the level of free cortisol in healthy horses, and determine if free cortisol levels were elevated in horses suffering from Pituitary Pars Intermedia Dysfunction (PPID) or Equine Metabolic Syndrome (EMS).
  • The researchers studied 57 healthy horses and 40 horses and ponies suffering from PPID (20) or EMS (20). They collected serum seasonally from the healthy animals and used archived serum from animals with PPID and EMS. The serum was analyzed for insulin and cortisol concentrations, and the free cortisol fraction (FCF).
  • Data analysis conducted using linear mixed models enabled the assessment of the effects of age, sex, season, and body condition on hormone levels in control subjects. Comparison of hormone measurements between disease groups and controls enabled further insights.

Results

  • The findings revealed that free cortisol concentrations were higher in overweight or obese control horses compared to their lean counterparts.
  • The mean FCF was significantly higher in horses with PPID or insulin dysregulation (hyperinsulinemia in PPID and EMS conditions) than in healthy control horses.
  • However, total cortisol concentrations were similar across groups, indicating that increased FCF is not due to an increased total cortisol production but could be due to a decreased plasma cortisol-binding capacity.

Conclusion

  • The study concludes that increased FCF is associated with obesity in healthy horses and with insulin dysregulation in animals suffering from endocrine disorders such as PPID and EMS.
  • This suggests that decreased plasma cortisol-binding capacity could play a role in these endocrine disorders in horses.

Cite This Article

APA
Hart KA, Wochele DM, Norton NA, McFarlane D, Wooldridge AA, Frank N. (2016). Effect of Age, Season, Body Condition, and Endocrine Status on Serum Free Cortisol Fraction and Insulin Concentration in Horses. J Vet Intern Med, 30(2), 653-663. https://doi.org/10.1111/jvim.13839

Publication

ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 30
Issue: 2
Pages: 653-663

Researcher Affiliations

Hart, K A
  • University of Georgia College of Veterinary Medicine, Athens, GA.
Wochele, D M
  • University of Georgia College of Veterinary Medicine, Athens, GA.
Norton, N A
  • University of Georgia College of Veterinary Medicine, Athens, GA.
McFarlane, D
  • Oklahoma State College of Veterinary Medicine, Stillwater, OK.
Wooldridge, A A
  • Auburn University College of Veterinary Medicine, Auburn, AL.
Frank, N
  • Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA.

MeSH Terms

  • Aging / blood
  • Animals
  • Body Composition / physiology
  • Case-Control Studies
  • Female
  • Horse Diseases / blood
  • Horse Diseases / metabolism
  • Horses
  • Hydrocortisone / blood
  • Insulin / blood
  • Male
  • Metabolic Syndrome / blood
  • Metabolic Syndrome / metabolism
  • Metabolic Syndrome / veterinary
  • Pituitary Diseases / blood
  • Pituitary Diseases / metabolism
  • Pituitary Diseases / veterinary
  • Seasons

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