Determination of Method-specific Normal Cortisol and Adrenal Hormone Responses to the Short Synacthen Test

Objectives: To establish valid serum total cortisol and salivary cut-offs for use with the short Synacthen test in patients with normal CBG concentrations. To investigate, using current assays, the effect of assay differences on the serum total cortisol cut-off. To explore the performance of these cut-offs in groups of patients with suspected adrenal insufficiency and high and low serum CBG concentration. Methodology: An ACTH test (250 micrograms iv ACTH1-24) will be undertaken in healthy volunteers, women taking an oestrogen-containing oral contraceptive pill (OCP), patients with adrenal insufficiency and patients with low serum albumin. Serum cortisol in the samples collected from healthy volunteers will be measured using GC-MS, Advia Centaur (Siemens), Architect (Abbott), Modular Analytics E170 (Roche), Immulite 2000 (Siemens) and Access (Beckman) automated immunoassays. The estimated lower reference limit for the 30 min cortisol response to ACTH, defined as the 2.5th percentile of log-transformed concentrations, will be determined in this healthy population and used as a cut-off in the patient groups studied.