====== Cushing's syndrome diagnosis =====

Due to high [[morbidity]] and [[mortality]] of untreated [[hypercortisolism]], a prompt diagnosis is essential.

[[Cushing's syndrome]] is usually easy to diagnose clinically owing to its characteristic features.

===== Laboratory tests =====

8 A.M. cortisol is the best test for [[hypocortisolism]] (e.g. to look for pituitary insufficiency); 24-hour urine free cortisol is the best test for hypercortisolism  
----

Morning and midnight serum cortisol levels

24h urine free cortisol excretion

11 PM [[salivary cortisol]]: this is the time of the usual cortisol nadir. Test must be run at NIH approved
lab. Accuracy is as good as low-dose [[Dexamethasone suppression test]]


Serum cortisol levels after low (1 mg) and high (8 mg) dexamethasone

The [[dexamethasone suppression test]] (DST) is used to assess adrenal gland function by measuring how cortisol levels change in response to an injection of dexamethasone. It is typically used to diagnose [[Cushing's syndrome]].

Plasma ACTH and serum cortisol levels after Desmopressin stimulation test
((Leal-Cerro A, Martín-Rodríguez JF, Ibáñez-Costa A, Madrazo-Atutxa A,
Venegas-Moreno E, León-Justel A, García-Hernández N, Luque RM, Castaño JP, Cano
DA, Soto-Moreno A. Desmopressin test in the diagnosis and follow-up of cyclical
Cushing's disease. Endocrinol Nutr. 2014 Feb;61(2):69-76. doi:
10.1016/j.endonu.2013.04.017. Epub 2013 Oct 30. English, Spanish. PubMed PMID:
24183946.
)).

Magnetic resonance imaging (MRI)  



Anatomical localization of source of excess ACTH [[Cushing's disease]] can be quite challenging. Sometimes, it becomes very difficult to differentiate ectopic ACTH source from Cushing's disease
((Ezzat S, Asa SL, Couldwell WT, Barr CE, Dodge WE, Vance ML, et al. The prevalence of pituitary neuroendocrine tumors: A systematic review. Cancer. 2004;101:613–9.))
((Utz A, Biller BM. The role of bilateral inferior petrosal sinus sampling in the diagnosis of Cushing's syndrome. Arq Bras Endocrinol Metabol. 2007;51:1329–38.)).

Subsequent to the diagnosis of ACTH-dependent Cushing's syndrome, the next step involves anatomical localization of the source of the ACTH secretion. Various biochemical and radiological techniques have been established to help in localization of the neoplastic lesion. Radiological techniques including [[computed tomography]] (CT)/magnetic resonance imaging (MRI) have poor sensitivity (around 60%)
((Aron DC, Raff H, Findling JW. Effectiveness versus efficacy: The limited value in clinical practice of high dose dexamethasone suppression testing in the differential diagnosis of adrenocorticotropin-dependent Cushing's syndrome. J Clin Endocrinol Metab. 1997;82:1780–5.)).

===== Salivary cortisol test=====

see [[Salivary cortisol test]]


====References====