Seasonal and pulsatile dynamics of thyrotropin and leptin in mares maintained under a constant energy balance.

This study sought to understand if there were differing levels of thyrotropin (TSH) and leptin in horse plasma due to seasonal changes while keeping energy intake consistent. It was found that during summer, levels of TSH and leptin were higher than in winter, implying that seasonal changes may affect the regulation of these hormones.

Objective of the Research

• The primary aim of this research was to identify if there is a seasonal and/or pulsatile variation in the plasma concentrations of thyrotropin (TSH) and leptin in mares under a consistent energy balance.

Methodology

• The study involved collecting blood samples from six Quarter Horse type mares every 20 minutes over a 24-hour period in winter and again in summer.
• The plasma concentrations of TSH, leptin, and T(4) were determined by performing a radioimmunoassay.
• The researchers maintained the horses’ body weights roughly the same in both seasons.

Findings

• The study did not find any significant difference in body weight between winter and summer.
• However, plasma concentrations of TSH were found to be significantly higher in summer as compared to winter.
• Although the pulse frequency of TSH didn’t differ across seasons, the average TSH pulse amplitude, pulse area, and area under the curve were all greater during summer compared to winter, providing evidence of a seasonal influence on TSH.
• The average concentrations of leptin were also found to be higher in summer than in winter, but there were no observed pulsatile secretion patterns of leptin in any of the horses.
• Conversely, the mean concentrations of T(4) were greater in winter than in summer.

Conclusion

• The observed seasonal differences in TSH and leptin concentrations provide evidence of potential seasonal regulation of these hormones.
• These findings could pave the way for further studies to explore the mechanism behind the seasonal regulation of TSH and leptin, which could have implications for equine health and wellbeing.