Concentrations of circulating gonadotropins during various reproductive states in mares.

The research focuses on measuring the concentration of gonadotropins, specifically FSH and LH hormones, in mares during their reproductive cycle. The result shows a non-significant difference between pony and horse mares and a correlation of these hormones with different stages of the cycle.

Measurements of Gonadotropins

• In this study, researchers examined the levels of FSH (follicle-stimulating hormone) and LH (luteinizing hormone), two types of gonadotropin hormones, in the bloodstreams of both pony and horse mares throughout their estrous cycle.
• These gonadotropins are hormones that play crucial roles in the reproductive process by primarily regulating the function of the ovaries.

Observations in Estrous Cycle

• Detailed observation of the estrous cycle revealed that FSH and LH were secreted in a reciprocal pattern. FSH levels were higher during the diestrus stage, whereas LH levels were higher during the estrus stage.
• Interestingly, the secretion patterns of FSH and progesterone were similar. However, the FSH level increased before progesterone at the end of estrus, suggesting that the initial increase of FSH might not be due to a progesterone-induced positive feedback mechanism.

Differences between Nonpregnant and Pregnant Mares

• As the study continued, a divergence in the patterns of LH secretion became noticeable between nonpregnant and pregnant mares approximately 19 days post-ovulation. This divergence was only observed with LH secretion and not with FSH.
• In both pregnant and hysterectomized mares, an elevation in FSH concentrations was noted after the end of estrus, mirroring patterns observed during diestrus.

Effects of Estradiol and Clomiphene Citrate Treatment

• The researchers also conducted a separate trial where diestrous mares were treated with estradiol and seasonally anovulatory mares were treated with clomiphene citrate. Clomiphene citrate is a medication used to treat infertility in women, as it is known to stimulate increased secretion of FSH and LH.
• However, these treatments did not show a significant effect on the concentrations of circulating FSH or LH hormones in the mares.