Plasma concentrations of testosterone and 19-nortestosterone (nandrolone) in the nonracing intact male horse by liquid chromatography-mass spectrometry.

The research explores the concentrations of testosterone and nandrolone in intact male horses, assessing these levels via liquid chromatography-mass spectrometry. It emphasizes the importance of monitoring these levels for regulation purposes in equine sports and suggests a withdrawal period for the usage of anabolic steroids.

Understanding Steroids in Equine Athletes

• The Commonwealth of Pennsylvania seeks to control the use of anabolic and androgenic steroids in equine sports by monitoring plasma samples from horses after competitions.
• Monitoring plasma is preferred over urine as the pharmacological action of drugs is reflected more accurately in plasma. Additionally, the complex excretion pattern of anabolic and androgenic steroids makes urine analysis more challenging.
• Testosterone and nandrolone, which are naturally produced in intact male horses in measurable quantities, become crucial parameters in maintaining competition fairness.
• The researchers recommend a minimum of 120 days withdrawal period following multiple administrations of anabolic steroids based on anecdotal information and initial observations.

Understanding Testosterone and Anabolic Steroids

• Anabolic steroids are synthetic derivatives of testosterone, promoting protein synthesis, muscle growth, and erythropoiesis – production of red blood cells. These effects can potentially enhance athletic performance, making regulation necessary in equine sports.
• The dominant androgenic steroid in intact male horses is testosterone. Other androgenic steroids found in significant quantities include androstenedione, dihydrotestosterone, dehydroepiandrosterone, and androstanediol.
• Quantification of androgenic steroids is done primarily through radioimmunoassay, but it is not as specific as direct measurement via liquid chromatography-mass spectrometry.

Observed Concentrations and Variances

• Plasma testosterone concentrations average 2000 pg ⁄mL in mature males, with concentrations fluctuating between 65 to 1600 pg ⁄mL in intact males and 15.3 ± 4.9 pg ⁄mL in geldings.
• Testosterone levels showed seasonal variation with a low in January (200 ± 100 pg ⁄mL) to a high in April (1400 ± 300 pg ⁄mL) and diurnal variation, with levels lower at 18 h.
• Stallions possess androgen-to-estrogen conversion abilities, meaning they produce estrogens since testosterone can be converted to estrogen by horse testicles.
• The administration of human chorionic gonadotrophin in horses triggers a rise in testosterone and estrogen, but this effect is not seen in geldings.