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Estrous cycle-dependent changes in platelet indices in healthy mares
Katiuska Satué1, Esterina Fazio2, Rocío Colomer-Selva1
1Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, CEU- Cardenal Herrera University, Tirant lo Blanc, 7, Alfara del Patriarca, Valencia, 46115, Spain.
Veterinary Research Communications
|June 6, 2026
Summary
Platelet indices in mares change during the estrous cycle, with larger, more variable platelets observed during diestrus. These changes correlate with fluctuations in estradiol and progesterone levels.
Area of Science:
- Veterinary Science
- Hematology
- Reproductive Biology
Background:
- Platelets (PLTs) are crucial for hemostasis, inflammation, and tissue repair.
- Sex steroid concentrations are known to influence platelet phenotype in various species.
- The impact of the estrous cycle on equine platelet characteristics remains understudied.
Purpose of the Study:
- To investigate variations in platelet indices during different phases of the estrous cycle in mares.
- To correlate these platelet parameters with circulating concentrations of estradiol-17β (E2) and progesterone (P4).
Main Methods:
- Evaluation of platelet indices in 25 healthy cyclic mares during estrus and diestrus.
- Measurement of quantitative and qualitative platelet parameters using an ADVIA 2120i analyzer.
- Quantification of plasma E2 and P4 concentrations via ELISA and RIA.
Main Results:
- Platelet count, plateletcrit (PCT), mean platelet mass (MPM), and mean platelet component (MPC) did not significantly differ between estrus and diestrus.
- Mean platelet volume (MPV), large platelets (PLCR), platelet aggregation (AGREG), and heterogeneity indices (PDW, PCDW, PMDW) were significantly higher during diestrus.
- Positive correlations were observed between ovarian steroids (especially P4) and indices of platelet size and heterogeneity.
Conclusions:
- Equine platelet indices exhibit variations across the estrous cycle.
- These changes are associated with fluctuations in circulating ovarian steroids, particularly progesterone.
- The findings suggest a hormonal influence on platelet characteristics in mares during their reproductive cycle.
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