Method‐specific serum cortisol responses to the adrenocorticotrophin test: comparison of gas chromatography‐mass spectrometry and five automated immunoassays

Normal cortisol responses to the ACTH test are influenced significantly by assay and oestrogen treatment. We recommend the use of separate reference limits in premenopausal women on the OCP and warn users that cortisol measurements in this subgroup are subject to assay interference.