Patterns of secretion of luteinizing hormone, follicle stimulating hormone and testosterone in stallions during the summer and winter.

The paper investigates the secretion patterns of luteinizing hormone, follicle stimulating hormone, and testosterone in stallions during summer and winter, including their interrelation and variance. It noted that secretion patterns remained generally constant across seasons, and that the concentrations of gonadotropins and testosterone present a significantly less pulsatile manner in stallions compared to males in other domestic species.

Research Design

• The researchers collected blood samples from five stallions every 15 minutes for 12 hours, during both summer and winter seasons.
• The samples were analyzed for plasma concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), and testosterone.
• The study sought to examine the short-term fluctuations in these hormone concentrations.

Research Findings

• Although LH and FSH concentrations were not generally pulsatile, a pattern of three distinct hormone pulses was identified in one stallion during winter.
• The secretion patterns of all three hormones were found to be similar across both seasons, with no significant difference in the number of rises in hormonal concentrations.
• There was a close relationship (correlation) between LH and FSH secretion rates in eight of the ten sampling periods.
• The testosterone concentrations showed episodic variation during the 12-hour period, with each stallion exhibiting at least one period of high secretion, independent of the LH concentration pattern.
• The correlation between a single random sample and mean concentrations over the 12-hour period was high (r between .88 and .99) for all three hormones, which suggests that a single blood sample could effectively represent overall concentrations.

Significance and Implications

• The study highlights the unique hormonal secretion pattern in stallions, differing from other male domestic species by showing less pulsatile variations in gonadotropins and testosterone levels.
• The strong correlation between single sample and mean concentration suggests that regular monitoring of hormone levels in stallions could potentially be conducted with a reduced number of samples, simplifying the process and reducing stress on the animals.
• The findings also provide a better understanding of the hormonal regulation in stallions, which could have implications in veterinary medicine and animal husbandry.