The extraction of cortisol from fingernails represents a recent advancement in the retrospective, long-term assessment of hypothalamic-pituitary-adrenal (HPA) axis activity: Fingernail cortisol has the potential to overcome some of the major disadvantages of established HPA axis markers. However, the introduction of any novel methodology also raises certain caveats. This review provides a comprehensive summary of the current state of research on fingernail cortisol. It identifies a number of strengths of his novel methodology (e.g., its high feasibility), while also pointing out open questions which currently challenge the interpretability of fingernail findings, in particular regarding the time period of cortisol secretion reflected in fingernail samples, as well as regarding potential determinants or confounders of fingernail cortisol (e.g. sociodemographic, lifestyle, or health characteristics). Clarification of these issues in the context of further methodological studies is necessary to validate the use of fingernail cortisol as a retrospective marker of HPA axis activity.

中文翻译：

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指甲皮质醇——研究现状和未来方向

从指甲中提取皮质醇代表了对下丘脑-垂体-肾上腺 (HPA) 轴活动的回顾性长期评估的最新进展：指甲皮质醇有可能克服已建立的 HPA 轴标记的一些主要缺点。然而，任何新方法的引入也会引起某些注意事项。本综述对指甲皮质醇的研究现状进行了全面总结。它确定了他的新方法的许多优势（例如，它的高可行性），同时也指出了目前挑战指甲发现的可解释性的开放性问题，特别是关于指甲样本中反映的皮质醇分泌的时间段，以及关于指甲皮质醇的潜在决定因素或混杂因素（例如 社会人口统计学、生活方式或健康特征）。在进一步的方法学研究的背景下澄清这些问题对于验证使用指甲皮质醇作为 HPA 轴活动的回顾性标记是必要的。