Effect of pulsatile or continuous administration of GnRH on reproductive function of stallions.

The research study investigates the impact of two methods of administering the Gonadotrophin-releasing hormone (GnRH) – pulsatile and continuous – on the reproductive function of stallions. The study concluded that while pulsatile administration could increase luteinizing hormone (LH) and potentially testosterone production, it did not lead to an increase in testicular size or the quantity and motility of sperm.

Methodology

• In this study, GnRH was administered subcutaneously to stallions that were reproductively both normal and abnormal. 6 normal horses received it in a pulsatile manner and another 6 received a continuous infusion. Meanwhile, 9 abnormal horses were also given GnRH in a pulsatile manner.
• The study was conducted from February to July 1988, during which the hormonal secretion patterns, testicular parameters, and semen characteristics of the stallions were monitored before and during the treatment period.

Findings

• Pulsatile GnRH increased the luteinizing hormone (LH) concentrations in the peripheral blood of normal stallions significantly.
• LH levels in abnormal stallions also gave a hint of an increase, though not significant.
• There was no recorded increase in LH concentrations in stallions given a continuous GnRH infusion and in untreated control stallions during the treatment period.
• None of the treatments led to a significant increase in peripheral blood concentrations of testosterone, even though individual stallions that showed increased LH secretion also showed some increase in testosterone secretion rate.
• No treatment led to increased total scrotal width, total number of spermatozoa per ejaculate, or the percentage of progressively motile spermatozoa in the ejaculate, for either individual stallions or in general.

Conclusion

• The research concludes that although pulsatile administration of GnRH may bolster the secretion rate of LH and, possibly, testosterone, this adjustment does not escalate testicular size or output and motility of spermatozoa.