Detection of doping with steroids that are also endogenous in the horse can be challenging, and a variety of approaches to distinguish exogenous administration from their natural presence are employed. Knowledge of endogenous concentrations of various steroids in different genders of horses (intact male, castrated male and female) and factors that could naturally affect them is beneficial for establishing ways for detection of their use. The current internationally adopted approaches include concentration-based thresholds in urine and plasma, steroid ratios in urine and targeting the administered intact steroid esters in plasma and hair. However, these have their limitations, and therefore, other strategies, such as additional biomarkers and steroid profiling based on longitudinal testing and multivariate analysis, have been investigated and could potentially improve detection of the use of endogenous steroids in horses. This paper aims to provide a comprehensive overview of the steroids (androgens, oestrogens and progestogens) that have been reported to be endogenous to horses in literature, their concentration ranges in different genders and factors potentially affecting them as well as current and possible future approaches to detect their use.

中文翻译：

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马内源性类固醇的存在和检测——综述


检测马内源性类固醇的掺杂可能具有挑战性，并且采用了多种方法来区分外源性施用与其天然存在。了解不同性别的马（完整的雄性、阉割的雄性和雌性）中各种类固醇的内源浓度以及可能自然影响它们的因素，有利于建立检测其使用的方法。目前国际上采用的方法包括基于尿液和血浆浓度的阈值、尿液中类固醇比率以及针对血浆和头发中施用的完整类固醇酯。然而，这些都有其局限性，因此，其他策略，例如基于纵向测试和多变量分析的额外生物标志物和类固醇分析，已经被研究，并且可能改善对马内源性类固醇使用的检测。本文旨在全面概述文献中报道的马内源性类固醇（雄激素、雌激素和孕激素）、它们在不同性别中的浓度范围和可能影响它们的因素，以及当前和未来可能的方法检测它们的使用。