Effect of stress on steroid hormone levels in racehorses.

The research article investigates the effect of stress on the levels of certain hormones (cortisol and testosterone) in racehorses. Higher levels of stress were found to significantly lower the levels of testosterone but not cortisol.

Research Methods

• The hormones cortisol and testosterone were measured in racehorses using a technique known as a radioimmunoassay. This technique involves using radioactive substances to measure the concentration of specific components (in this case, the hormones) in plasma samples.
• The study focused on male racehorses, where six of them were subjected to stress.

Findings

• The researchers found that none of the stressed horses had low cortisol levels. This means that the level of cortisol, a hormone related to stress, did not decrease under stress.
• On the other hand, testosterone levels in the stressed horses were significantly lower than what was observed in healthy horses. The testosterone levels in stressed horses were about less than half of the levels in healthy horses, indicating that stress significantly impacts testosterone levels.

Conclusion

• The researchers concluded that adrenocortical insufficiency (a condition characterised by a decreased production of hormones by the adrenal glands) is not commonly associated with stress in racehorses. In other words, the stress experienced by racehorses does not lead to a significant reduction in cortisol levels.
• However, the reduction in testosterone levels under stress was identified as a nonspecific response observed not just in racehorses, but also in other species under stress. This suggests a common physiological response to stress across various species, where testosterone levels tend to decline.