Influence of season and pituitary pars intermedia dysfunction on hair cortisol concentration in horses.

The research article discusses how the season and pituitary dysfunction affects the amount of cortisol in horse hair. The study found that horses with pituitary pars intermedia dysfunction (PPID) had higher levels of cortisol in their hair during the fall season compared to healthy horses.

Research Context and Hypothesis

• The research was conducted to test the hypothesis that cortisol concentration in horse hair are higher in horses with pituitary pars intermedia dysfunction (PPID) in comparison with healthy horses. Furthermore, this difference was expected to be larger during the fall season due to higher circulating levels of the hormone adrenocorticotropin (ACTH).
• The adrenal glands produce the hormone cortisol, which is a reliable measure of stress and health conditions, such as Cushing’s disease. ACTH, another hormone secreted by the pituitary gland stimulates the production of cortisol.
• PPID is a disease in horses characterised by an enlarged and overactive pituitary gland resulting in an overproduction of ACTH.

Research Methodology

• Hair samples were collected using clippers from the neck of PPID and healthy, control horses during several months in the fall season and once in the spring.
• The sites of hair sample collections included the neck, jugular furrow, sternum, and submandibular regions. Six horses with PPID and eight control horses were used for the study.
• The study investigated the relationship between ACTH and hair cortisol concentrations during the fall months.

Research Findings

• Cortisol concentration measured by weight was significantly higher in horses with PPID as compared to the control horses in the months of October and November, but not in December, May or August-September.
• When the cortisol concentration was balanced for hair length, higher levels were found in PPID horses only in November.
• No significant differences were found between PPID and control horses in hair cortisol concentrations from any collection site in May.
• No consistent relationships were found between the hormone ACTH and hair cortisol concentrations in the fall months.

Conclusion and Future Perspectives

• The study concludes that horses with PPID have an increased accumulation of hair cortisol in the fall as compared to healthy or control horses.
• However, further research is required to understand if hair cortisol should be assessed per weight or per hair length to be most relevant in horses.