7692 Morning Cortisol Levels In Patients With Established Primary Adrenal Insufficiency

Abstract Disclosure: A. Prete: Research Investigator; Self; Diurnal. V. Theiler-Schwetz: Research Investigator; Self; Diurnal. W. Arlt: Research Investigator; Self; Diurnal. I.O. Chifu: Research Investigator; Self; Diurnal. B. Harbeck: Research Investigator; Self; Diurnal. C. Napier: Research Investigator; Self; Diurnal. J.D. Newell-Price: Research Investigator; Self; Diurnal. A. Rees: Research Investigator; Self; Diurnal. N. Reisch: Research Investigator; Self; Diurnal. G.K. Stalla: Research Investigator; Self; Diurnal. N. Aslam: Employee; Self; Diurnal. H. Coope: Employee; Self; Diurnal. K. Maltby: Employee; Self; Diurnal. J. Porter: Employee; Self; Diurnal. J. Quirke: Employee; Self; Diurnal. R.J. Ross: Consulting Fee; Self; Diurnal. Background: Primary adrenal insufficiency (PAI) is rare: prevalence ∼100-140/million and incidence 4:1 000 000/year in Western societies [1]. The diagnosis of PAI is suggested by an early-morning cortisol <140 nmol/L (5 µg/dL) [1]. The commonest cause in adults is autoimmunity (∼90% in Western countries) and it is generally considered progressive once the diagnosis is made, although it has been reported that residual cortisol secretion is present in ∼30% of patients 2. We have developed a modified-release formulation of hydrocortisone to replace the physiological cortisol circadian rhythm and are undertaking a Double-Blind, Double-Dummy, Two-Way Cross-Over, Randomised, Phase II Study of Modified-Release Hydrocortisones: Chronocort® Versus Plenadren® in PAI. During recruitment, we were surprised by the number of patients who were ineligible as they had detectable morning cortisol levels. Methods: Main inclusion criteria: Participants with known PAI on stable glucocorticoid replacement therapy and an early morning pre-dose cortisol <50 nmol/L (1.8 µg/dl). Baseline serum cortisol was taken at ∼0700h and measured in a central laboratory by ADVIA Centaur® immunoassay with the lower limit of detection <14nmol/l (<0.5 µg/dL). Results: 86 patients with PAI (autoimmune aetiology in 71), median age 52 years (range 20-73), 60 female, were screened in 8 centres in UK and Germany. 18 (21%) patients were excluded from the study based on morning cortisol >50 nmol/L (1.8 µg/dL), and of those 68 patients who qualified on the main inclusion criteria 51 (59% of screened) had a cortisol <14 nmol/L (<0.5 µg/dL). Of the 18 patients (autoimmune aetiology in 10) excluded based on their morning cortisol level, 9 (50%) were female and 11 (13% of screened), had morning cortisol ≥140 nmol/L (5.0 µ/dL). 12 patients with morning cortisol of >50nmol/L (1.8 µ/dL) were retested and only 2 then qualified; their initial morning cortisol levels were 70 and 51 nmol/L. In patients retested the median difference between retest and the initial sample was 13 nmol/L (range 1-421 nmol/L). Conclusions: In patients with an established diagnosis of PAI, the majority had undetectable morning cortisol, but cortisol was detectable in 41% of patients and above 140 nmol/L in 13% confirming previous publications 2. Retesting patients with a cortisol >50nmol/L showed very similar results suggesting that the detectable cortisol was not an artefact and likely due to background cortisol secretion. 1. Bornstein SR, et al. J Clin Endocrinol Metab 2016;101:364-89.2.Pearce SHS, et al. European Journal of Endocrinology (2021) 184, R61–R67 Presentation: 6/1/2024