[The endocrine status of clinically conspicuous mares during the peripartum period].

The research article aims to study hormone changes in the blood of pregnant mares known to have complications during childbirth or abortion. The levels of various steroid hormones were measured before and after birth and while cortisol, DHEA, and transcortin generally did not change, others significantly decreased after birth. Even in mares with significant health problems, the hormones monitored did not indicate any pregnancy issues. The study suggests that monitoring estrone sulfate (E1-S) levels is the best indicator of a fetus’s well-being, although it may not predict the onset of birth or abortion.

Study Purpose and Methods

• The primary goal of this research was to identify changes in hormone levels in the peripheral blood of pregnant mares with previous obstetrical complications.
• The researchers collected blood plasma samples from 9 mares, including 8 shortly before and after childbirth and 1 during abortion.
• The team used a method called radioimmunoassay to measure hormone levels, specifically focusing on steroid hormones such as progesterone, dehydroepiandrosterone (DHEA), DHEA-sulfate (DHEA-S), estrone (E1), estrone sulfate (E1-S), estradiol-17 beta (E2), estriol (E3), cortisol, and transcortin.

Key Findings

• Most of the studied steroid hormone levels, except cortisol, DHEA, and transcortin, significantly decreased after parturition (birth).
• The mean blood plasma concentrations of DHEA-S, the direct precursor of estrone needed for fetus development, were observed to be six times higher than DHEA itself.
• The values of DHEA-S varied considerably both between different mares and within the same mare on different days.
• Concentrations of estrone sulfate (E1-S) were a thousand times higher than those of E1, E2, and E3.
• The researchers noted low concentrations of E3, suggesting it is primarily created by peripheral conversion and that the horse fetus likely lacks the 16 alpha-hydroxylation of DHEA-S.
• Despite most of the mares studied showing signs of severe illness, none of the hormonal measurements indicated any disruption of gestation, suggesting that these measurements are not reliable indicators of pregnancy complications.

Conclusions

• The researchers concluded that tracking changes in E1-S blood plasma levels could be an effective way to monitor fetal health.
• However, even variations in E1-S measurements can’t reliably predict the onset of parturition or abortion, underscoring the necessity for further study to find reliable biomarkers of these events.