Suspected Cushing's syndrome (hypercortisolism)
BioMG follows French guidelines. Adapt it to the guidelines and the tests available where you practise.
Clinical suspicion: screening
One first-line test, chosen depending on the context (see the note)
- 24-hour urinary free cortisol with urinary creatinine (2 collections)if neededObvious or severe form, without renal failure; can be used on oestrogens [1,2].
- 8 am serum cortisol after 1 mg of dexamethasone taken between 23 h and midnightif neededSubtle form, without oestrogens or any drug altering dexamethasone metabolism [1,2].
- Late-night salivary cortisol (2 samples, non-consecutive days)if neededWhen suppression testing or urinary free cortisol cannot be done (pill, renal failure) [1].
Also consider
- Corticosteroids by any route? Corticosteroid therapy must be excluded first, before any assay: see the page "Treatment: long-term corticosteroids".
- Adrenal tumour found? Every adrenal tumour must be investigated: see the page "Adrenal incidentaloma".
Do not order
- Routine screening in a patient with type 2 diabetes, obesity or hypertension without suggestive signs: not recommended (very low prevalence, many false positives) [1,2].
- Random blood cortisol or ACTH (including an isolated 8 am cortisol) to screen for Cushing's syndrome: not recommended [2].
- Urinary 17-ketosteroids: not recommended [2].
- ACTH and imaging (pituitary, adrenals) before hypercortisolism is confirmed: these are aetiological tests, not to be done as screening [1,2].
Abnormal test: confirm and guide
After confirmation of hypercortisolism (in liaison with the endocrinologist)
- Plasma ACTH between 8 am and 9 am, with serum cortisol on the same sample (2 samples)
Sources (6)
- Tabarin A, Assié G, Barat P, Bonnet F, Bonneville JF, Borson-Chazot F, et al. Consensus statement by the French Society of Endocrinology (SFE) and French Society of Pediatric Endocrinology & Diabetology (SFEDP) on diagnosis of Cushing's syndrome. Ann Endocrinol (Paris). 2022;83(2):119-141.
- Nieman LK, Biller BM, Findling JW, Newell-Price J, Savage MO, Stewart PM, et al. The diagnosis of Cushing's syndrome: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2008;93(5):1526-40.
- Assurance maladie. Nomenclature des actes de biologie médicale (NABM), version 105 : actes 0462 (cortisol sanguin), 0476 (cortisol libre urinaire), 0627 (créatininurie) et 7420 (ACTH).
- Fleseriu M, Auchus R, Bancos I, Ben-Shlomo A, Bertherat J, Biermasz NR, et al. Consensus on diagnosis and management of Cushing's disease: a guideline update. Lancet Diabetes Endocrinol. 2021;9(12):847-875.
- Lee J, Fukuoka H, Park SS, Hong AR, Kim JH, Chin SO, et al. Consensus on the diagnosis of Cushing's disease: a collaborative statement from the Korean Endocrine Society and Japan Endocrine Society. Endocrinol Metab (Seoul). 2026;41(1):1-13.
- Braun LT, Vogel F, Zopp S, Marchant Seiter T, Rubinstein G, Berr CM, et al. Whom should we screen for Cushing syndrome? The Endocrine Society practice guideline recommendations 2008 revisited. J Clin Endocrinol Metab. 2022;107(9):e3723-e3730.