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Testosterone secretion during early pregnancy in mares.
P F Daels1, G C Chang, B Hansen
1Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. pfd1@cornell.edu
Theriogenology
|April 15, 1996
Summary
The corpus luteum (CL) significantly influences testosterone levels in early pregnancy in mares before equine chorionic gonadotropin (eCG) secretion. Post-eCG, testosterone increase is linked to eCG-stimulated luteal synthesis.
Area of Science:
- Reproductive Endocrinology
- Equine Science
- Maternal-Fetal Physiology
Background:
- Testosterone plays a role in equine pregnancy.
- Understanding testosterone sources is crucial for early pregnancy monitoring.
Purpose of the Study:
- Characterize testosterone secretion patterns in early pregnancy (first 80 days) in mares.
- Identify the sources contributing to circulating testosterone levels during this period.
Main Methods:
- Studied three groups of pregnant mares: untreated, altrenogest-treated, and altrenogest-treated with corpus luteum (CL) elimination via PGF-2alpha.
- Analyzed testosterone concentrations relative to CL function and equine chorionic gonadotropin (eCG) secretion.
- Excluded mares that developed a new CL after initial luteolysis.
Main Results:
- Mares without a functional CL had significantly lower testosterone before eCG secretion.
- Testosterone increased rapidly with eCG onset in mares with a functional CL.
- Mares without a functional CL showed a delayed testosterone increase after Day 50, not correlating with eCG onset.
Conclusions:
- The CL is a significant source of circulating testosterone before eCG secretion.
- Increased testosterone after Day 35 is likely due to eCG-stimulated luteal synthesis.
- This highlights the dynamic interplay between CL, eCG, and testosterone during early equine pregnancy.