Effects of dihydrotestosterone benzoate administration on gonadotropin secretion in ovariectomized pony mares.

The research examines the impact of dihydrotestosterone benzoate on the secretion of certain hormones in mares previously subject to ovariectomy. The results suggest the substance cannot mimic testosterone’s stimulatory effects on hormone production and secretion as seen in prior experiments on intact and ovariectomized mares.

Research Methodology

• Eight long-term ovariectomized (ovaries removed) pony mares were chosen for the experiment.
• These mares were treated with either dihydrotestosterone (DHT) benzoate or an equal amount of oil (as control), every other day for 21 days.
• The main aim was to observe any changes in follicle stimulating hormone (FSH) and luteinizing hormone (LH) concentrations in the mares’ blood samples, due to the DHT treatment.
• Additionally, three successive injections of gonadotropin-releasing hormone (GnRH) were administered at four-hour intervals, after the last DHT or oil injection, to determine any reaction to the GnRH.

Findings

• DHT benzoate did not appear to have any significant influence on the FSH or LH concentrations when compared to the controls, as per the daily blood samples.
• The response of both FSH and LH (as measured by the areas under the GnRH curves) descended, statistically significantly, from the first to third GnRH injection across all the mares.
• No effect of the DHT treatment was noted on FSH response to GnRH.
• However, there was a significant interaction between treatment and GnRH injection for LH areas. Specifically, the LH areas declined significantly for the DHT-treated mares from the first to third GnRH injection, whereas no change was observed for the control mares.

Conclusion

• It was concluded that DHT alone isn’t able to emulate the stimulatory effects of testosterone on FSH production and secretion. This result contrasts with findings from past experiments involving ovariectomized and non-ovariectomized mares.
• Interestingly, intact (non-ovariectomized) mares in previous studies were shown to respond to DHT treatment with an increase in GnRH-induced FSH secretion. This indicates that a mechanism, which gets lost in mares after a long-term ovariectomy, is responsible for making them non-responsive to DHT treatment.