Seasonal variation in the feedback of sex steroid hormones on serum LH concentrations in the male horse.

The research article focuses on studying the potential seasonal variation in the feedback effect of sex hormones, specifically testosterone and oestradiol, on serum LH concentrations in male horses. The study suggests that testosterone’s feedback effect varies with season and its replacement can help replicate the stallion’s seasonal pattern of LH secretion, indicating that these hormones play an essential part in controlling seasonal breeding in male horses.

Research Method and Process

• The researchers investigate the potential seasonal variation in the feedback influence of two sex steroid hormones, testosterone and oestradiol, on serum LH (luteinizing hormone) concentrations in the male horse.
• This is done by administering replacement treatments to male horses that have been castrated (geldings) over a period of 2-3 weeks during both breeding and non-breeding seasons.

Findings and Conclusions

• In the non-breeding season, testosterone was found to suppress LH values in all geldings. However, during the early breeding season, testosterone caused an extended increase in LH.
• In all experiments involving testosterone, LH was observed to return to pre-treatment levels within two weeks after the treatment concluded.
• On the other hand, the treatment with oestradiol caused a prolonged increase in LH concentrations in both the breeding and the non-breeding seasons.
• The study concludes that the feedback effect of testosterone in geldings varies by season. Furthermore, testosterone replacement may be capable of reinstating the stallion’s seasonal pattern of LH secretion in geldings.
• The findings suggest that in male horses, testosterone, and possibly oestradiol, are vital components in the neuroendocrine pathway that controls seasonal breeding. They are also crucial for generating a positive signal for LH secretion during the breeding season.