Positive effect of FSH but not LH on early development of the dominant follicle in mares.

This study examines the influence of hormones FSH and LH on the growth of follicles, specifically the dominant follicle, in mares. The results show that FSH, not LH, significantly contributes to the early development and growth of the largest follicle in mares.

Research Methods

• The study involved an examination of the impact of Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH) on follicular growth and levels of intrafollicular free Insulin-like Growth Factor (IGF-1) and oestradiol in mares.
• The investigation began after the onset of deviation, which was defined as when the largest follicle reached a diameter greater or equal to 20mm (Hour 0).
• At Hour 3 following the onset of deviation, a Gonadotropin-releasing Hormone (GnRH) antagonist known as acyline was administered once to suppress FSH and LH concentrations.
• The study involved five groups of mares (n = 5 mares per group): control, acyline treated, acyline + recombinant equine (re) FSH treated, acyline + reLH treated, and combined acyline + reFSH + reLH treated.
• Starting at Hour 3, reFSH and reLH were given at 6-hour intervals in either increasing or decreasing doses respectively.
• The goal was to evaluate the influence of FSH and LH hormones on the process of follicular growth and development.

Findings and Conclusions

• The administration of reFSH and reLH successfully prevented the acyline-induced decrease in FSH and LH, respectively.
• The diameters and concentrations of intrafollicular free IGF-1 and oestradiol of the two largest follicles at Hour 48 showed no significant differences between the control and acyline + FSH groups. However, they were significantly reduced in the acyline and acyline + LH groups.
• The combined usage of reFSH and reLH was not more effective than using reFSH alone. This leads to the conclusion that FSH, not LH, significantly contributes to the early development of the largest follicle in mares.
• The findings suggested that FSH plays a key role in the growth of the dominant follicle and intrafollicular concentrations of free IGF-1 and oestradiol during the 48 hours following the beginning of deviation in mares. On the other hand, LH didn’t demonstrate a significant impact in the same context.