Assessment of endogenous growth hormone pulsatility in gelded yearling horses using deconvolution analysis.

The research investigates the normal growth hormone (GH) secretory dynamics in horses to better understand alterations linked to health and disease. It uses a deconvolution analysis method to gauge GH secretion in gelded yearling horses.

Research Methodology

• The study involved twelve yearling and two mature Standardbred horses. The GH secretion in these animals was quantified for the research.
• The endogenous GH’s half-life was determined after administering a 1.0 µg/kg BW GH-releasing hormone (GHRH), and exogenous GH half-life using 20 µg/kg BW recombinant equine GH (reGH).
• The research team also used somatostatin to suppress endogenous GH secretion and examine its effects on GH half-life.
• A pulse detection algorithm and deconvolution analysis were applied to quantify GH secretory dynamics based on GH concentration-time sequences acquired every five minutes from 10 PM till 6 AM.
• Further tests assessed the reproducibility, the impact of different sampling frequencies, and how altering the original GH half-life affected the estimates.

Results

• Endogenous GH was found to have a mean half-life of 17.7 ± 4.4 minutes while exogenous GH had a mean half-life of 26.0 ± 2.9 minutes.
• The mean number of GH secretion peaks in an 8-hour period was 12 ± 3.2.
• Almost all (99%) of GH secretion occurred in pulses, with basal secretion at 0.012 ± 0.014 µg/L/min and a half-life of 8.9 ± 2.6 minutes.
• Compared to a 5-minute sampling window, sampling every 20 or 30 minutes underestimated the number of secretory events by 45% and 100% respectively.

Conclusion

• The deconvolution model tested proved valid for GH time series in Standardbred horses.
• Similar to humans, the equine pituitary gland expresses GH in volleys of multiple secretory bursts rather than constant (or “tonic”) secretion.
• The optimal GH sampling frequency for horses appears to be around 3 minutes.
• The research’s findings contribute important data on normal GH secretory dynamics in horses, a crucial factor in understanding and identifying pathological alterations and potential abuse of recombinant equine GH.