Growth hormone (GH) secretory pattern and GH response to GH-releasing factor (GRF) or thyrotropin-releasing hormone (TRH) in newborn foals.

The research article investigates the growth hormone (GH) secretory patterns in newborn foals and their mothers, and how these hormones respond to GH-releasing factor (GRF) and thyrotropin-releasing hormone (TRH) over their first forty days after birth.

Objective

The objective of the study is to understand the pattern of GH secretion in newborn foals and their dams, and evaluate the impact of GRF and TRH on plasma GH concentrations during the first forty days after birth.

Methodology

• The study surveyed twelve light-breed foals and their dams.
• GH secretory patterns were assessed during the first day and the fortieth day after delivery.
• The influence of GRF and TRH on plasma GH concentrations in the foals was documented.
• Blood samples were collected every 20 minutes for 24 hours to measure mean daily plasma concentrations.
• The number and amplitude of GH secretory spikes were also recorded.

Findings

• The GH secretory pattern in the foals was found to be pulsatile on both the first and fortieth day.
• The number of secretory spikes remained constant, which indicates no circadian rhythm in either the foals or their dams.
• The daily mean plasma concentrations were lower in the mares (3.4 +/- 0.3 ng/ml) compared to their foals (7.4 +/- 0.9 ng/ml), attributed to a lesser number and lower amplitude of GH spikes.
• Synthetic human GRF significantly increased plasma GH concentrations in three-day and six-day-old foals, whereas TRH did not show any significant change.

Conclusion

This study concludes that the secretion of GH in newborn foals is regular and not influenced by the circadian rhythm. Additionally, GRF can increase the concentration of GH in the foals’ plasma, while TRH doesn’t seem to have a significant effect.