Cortisol is the most abundant circulating steroid and the major glucocorticoid secreted by the adrenal cortex. Physiologically effective in anti-inflammatory activity and blood pressure maintenance, cortisol is involved in gluconeogenesis, calcium absorption and the secretion of gastric acid and pepsin.
As an indicator of adrenocortical function, measurement of blood cortisol levels is useful in the differential diagnosis of Addisons and Cushings disease, hypopituitorism and adrenal hyperplasia and carcinoma.
A variety of stimulation and suppression tests (ACTH, dexamethasone) can supply supportive information on adrenocorticol function.
Urine: The determination of cortisol in 24 hour urine is the method of choice for the detection of Cushing′s syndrome since cortisol excretion in urine is not subject to the diurnal rhythm of cortisol secretion. Cortisol which is excreted into urine without alteration is referred to as urinary free cortisol (UFC).
CortisolResting Value (9:00 – 10:00): 119 – 618 nmol/L
Midnight Value: 85 – 459 nmol/L
Urine: 5 – 55 µmol/mol creatinine
Cortisol: 2 hours
Urine: 1 week