Changes Associated with the Peri-Ovulatory Period, Age and Pregnancy in ACTH, Cortisol, Glucose and Insulin Concentrations in Mares.
Authors: Hicks Gemma R, Fraser Natalie S, Bertin François-René
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Reproductive hormonal changes in mares are well documented, yet the influence of ovulation and early pregnancy on adrenocorticotropic hormone (ACTH) and insulin dynamics has remained largely unexplored—a gap this 2021 investigation addressed by monitoring 18 clinically healthy mares across their peri-ovulatory period using ultrasound and progesterone profiles to precisely time reproductive events. Researchers measured ACTH, cortisol, insulin and glucose concentrations at multiple timepoints, stratifying results by mare age and pregnancy status and employing two-way repeated-measures analysis to isolate the effects of these variables. Whilst cortisol, insulin and glucose concentrations remained stable regardless of reproductive stage or age, ACTH concentrations demonstrated significant fluctuations both around ovulation and during early pregnancy (p = 0.04 for both), indicating that the hypothalamic-pituitary-adrenal axis responds measurably to reproductive events. For equine practitioners interpreting ACTH levels—particularly those screening for pituitary pars intermedia dysfunction—this finding carries important implications: a mare's position within her oestrous cycle or early gestational status must be factored into diagnostic decision-making to avoid misattributing physiologically normal reproductive-related ACTH elevation to endocrine pathology.
Read the full abstract on PubMed
Practical Takeaways
- •ACTH results should be interpreted with consideration of a mare's reproductive cycle and pregnancy status, as these factors can alter values independently of PPID
- •Clinicians should account for peri-ovulatory and early pregnancy phases when screening for endocrine disorders in breeding mares to avoid misdiagnosis
- •Cortisol, insulin, and glucose concentrations remain stable through reproductive cycles and early pregnancy, so these markers are more reliable for metabolic assessment
Key Findings
- •ACTH concentrations show significant changes around ovulation (p = 0.04) and with early pregnancy (p = 0.04) in healthy mares without PPID or insulin dysregulation
- •Age, ovulation, and early pregnancy do not significantly affect cortisol, insulin, or glucose concentrations in this population
- •Knowledge of reproductive status is beneficial when interpreting ACTH concentrations in mares