Monitoring dehydroepiandrosterone (DHEA) in the urine of Thoroughbred geldings for doping control purposes.

The study investigates urinary levels of the hormone dehydroepiandrosterone (DHEA) in Thoroughbred geldings for the purpose of doping control, relevant in determining whether the horse has been administered testosterone or DHEA, which are regulated substances in horse racing.

Objectives and Methods

• The research aimed to advance current doping control methods in horse racing by exploring additional approaches. These included steroid ratios and longitudinal steroid profiling of individual animals, also known as an equine biological passport.
• The study analysed DHEA concentrations and related ratios (testosterone [T] to DHEA and DHEA to epitestosterone [E]) in 200 post-race gelding urine samples. The urine samples were analysed using liquid chromatography-tandem mass spectrometry.

Results

• The results found DHEA concentrations ranging between 0.9 and 136.6 ng/mL and T:DHEA ratios between 0.06 and 1.85, and DHEA:E ratios between 0.21 and 13.56.
• Statistical upper limits were proposed for the T:DHEA ratio (5.4) and the DHEA:E ratio (48.1), with a risk of 1 in 10 000 for a normal outlier exceeding the value.
• Further analysis of post-administration urine samples taken after administrations of DHEA, Equi-Bolic® (a mix of DHEA and pregnenolone) and testosterone propionate showed that the upper limit for T:DHEA ratio was exceeded following testosterone propionate administration and DHEA:E ratio following DHEA administrations.

Implications

• These findings suggest that these ratios could serve as additional biomarkers in determining the source of an atypical testosterone concentration in geldings.
• Moreover, DHEA concentrations and ratios can form a basis for establishing reference ranges for an equine biological passport – a longitudinal profile that could aid in more accurate and individualised doping controls in horse racing.