[Reference values for cortisol, T4 and T-uptake in different horse groups using the fluorescence polarization immunoassay (FPIA)].

The research study establishes reference values for cortisol, T4, and T-uptake in the blood plasma of various groups of horses, using Fluorescence-Polarization-Immunoassays (FPIAs). It evaluates the highest and lowest values of cortisol and the peak values for T4 across different times of day, and observes no diurnal variation for T-uptake.

Objective of the Study

• The aim of this research was to establish reference values for cortisol, T4, and T-uptake levels in the blood plasma of multiple horse groups. The measurements were carried out with Fluorescence-Polarization-Immunoassays (FPIAs).

Cortisol Values

• The highest concentrations of cortisol were reported in samples from thoroughbred racehorses and riding horses collected from 7 to 8 am, while the lowest concentrations were observed between 5 and 6 pm.
• The findings indicate that cortisol levels in horses demonstrate a diurnal variation, i.e., they change depending on the time of day.

T4 Values

• Peak values for T4 in riding horses were found in the blood samples taken between 1 and 2 pm, followed by the samples collected at 5-6 pm and 7-8 am.
• It seems that T4 levels in horses, similar to cortisol, display a time-dependent pattern, although the pattern is not the same.

T-uptake Values

• T-uptake levels were not affected by the time of day, displaying no diurnal variation.
• The levels of T-uptake in thoroughbred racehorses were significantly lower than those in thoroughbred broodmares and riding horses, indicating that T-uptake rates may vary between different breeds or types of horses.

Stability of Hormone Values over Days

• The study found noticeable changes in cortisol levels in the blood samples collected over five successive days.
• In contrast, T4 values remained stable, and T-Uptake showed only minor variations across the same period.

In summary, this study provides crucial insights into the patterns and levels of certain hormones in the blood of different horse groups, which may assist in the better understanding of horse physiology and healthcare.