Treatment with human chorionic gonadotropin (hCG) for ovulation induction is associated with an immediate 17beta-estradiol decrease and a more rapid LH increase in mares.

This research investigates the effect of a dose of human chorionic gonadotropin, a hormone used to induce ovulation, on the levels of certain hormones in horses. It found that the treatment quickly reduces the level of one hormone (17beta-estradiol) and rapidly increases another (LH).

Overview of Experiment 1

• Initial experiment examined the impact of hCG treatment on the ovulation process in mares.
• It was observed that ovulation generally occurred around 48 hours post-treatment.
• Further analysis showed no significant difference in changes to LH, a hormone at the center of ovulation, and estradiol, a form of estrogen, between mares that received hCG treatment (n=15) and those that did not (control group, n=13).

Overview of Experiment 2

• This experiment tracked more detailed fluctuations in hormone levels after hCG treatment.
• hCG levels were observed to drop drastically, by 92%, in the 1 to 48 hours following treatment.
• Within six hours, there was a marked decrease in estradiol levels, with statistical significance (P<0.003)
• Furthermore, the rate of increase in LH levels after 12 hours was notably greater (P<0.02) (n=14).

Key Findings and Conclusions

• Overall findings suggest that hCG treatment leads to a rapid decrease in estradiol and a correspondingly swift increase in LH rates.
• In relation to ovulation, the research found no significant difference in LH surges and drops in estradiol between hCG-treated groups and control groups.