Dose-response effects of gonadotropin-releasing hormone on plasma concentrations of gonadotropins and testosterone in fertile and subfertile stallions.

This research is a study of the effects of gonadotropin-releasing hormone on concentrations of gonadotropins and testosterone in horses, specifically comparing fertile and subfertile stallions. The findings show different hormonal responses in these two groups.

Overview of the Experiment

• The researchers included a total of ten stallions in their study, five that were fertile and the other five which were infertile.
• The study began with an injection of saline into the horses in the first week. This was followed by administration of varying doses of gonadotropin-releasing hormone each week for the next five weeks.
• Blood samples were taken before and after the treatment from each stallion and examined for levels of luteinizing hormone, follicle stimulating hormone, and testosterone.
• Before starting the treatment, the semen from each horse was collected every other day for 3 weeks. The traits recorded from these samples include the overall volume, concentration, motility, pH, and morphology.

Analysis and Findings

• Before starting treatment, it was observed that the subfertile group had generally higher levels of luteinizing hormone and follicle stimulating hormone when compared to the fertile group. The two groups, however, had comparable testosterone levels.
• Upon administration of the gonadotropin-releasing hormone, both groups exhibited a dose-response relationship in terms of luteinizing hormone and follicle stimulating hormone. This means that as the dose of the hormone increased, the plasma concentrations of these hormones also increased, showing the hormonal response of the bodies of both fertile and subfertile stallions to the gonadotropin-releasing hormone.
• The same dose-response relationship was noticeably evident for testosterone in the fertile group but was not present in the subfertile group.
• Moreover, after the treatment, the testosterone levels in terms of both net increase and percentage of the baseline were considerably lower in the subfertile group as opposed to the fertile group. This indicates that the gonadotropin-releasing hormone had a different effect on the two groups of stallions.