Hardaker, NJHume, PASims, STStewart, TKing, DA2025-12-082025-12-082025-05-05Experimental Physiology, ISSN: 0958-0670 (Print); 1469-445X (Online), Wiley. doi: 10.1113/EP0925420958-06701469-445Xhttp://hdl.handle.net/10292/20346Blood-based measures are considered the gold standard for evaluating steroid hormone concentrations, particularly for confirmation of hormone profiles in female-specific research. However, saliva sampling offers several advantages: it can be collected independently by participants, is less invasive and might be a more time- and cost-effective solution. This preliminary study explored associations between salivary and blood plasma hormone (oestrogen, progesterone and cortisol) concentrations using an automated electrochemiluminescence immunoassay technique. Eight healthy, physically active females with a regular natural menstrual cycle provided: (1) daily app-based menstrual tracking data; (2) daily saliva samples; and (3) two blood samples, each at different time points in the third to fifth menstrual cycle estimated using the backward calculation method. Associations between saliva and blood hormone concentrations were analysed using repeated-measures correlations. Progesterone and oestrogen showed positive associations between blood plasma and salivary measures; (rm= 0.996, p < 0.0001 and rm= 0.705, p = 0.0507, respectively). Weak non-significant associations for cortisol (rm= 0.245, p = 0.526) were found. With further work to validate the assay and develop salivary reference ranges, the electrochemiluminescence immunoassay technique might be feasible for use in quantitative determination of progesterone and oestrogen in saliva and have application in research for within-participant monitoring of changes over time.© 2025 The Author(s). Experimental Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.http://creativecommons.org/licenses/by/4.0/electrochemiluminescencesalivasex hormone32 Biomedical and Clinical Sciences3202 Clinical SciencesContraception/ReproductionClinical ResearchMetabolic and endocrine0606 Physiology1106 Human Movement and Sports Sciences1116 Medical PhysiologyPhysiology3109 Zoology3208 Medical physiology4207 Sports science and exerciseJournal ArticleOpenAccess10.1113/EP092542