Department

Biochemistry
24 hour collection (minimum sample volume 500 uL)

Sample Processing in Laboratory

Usual

Sample Preparation

A 24 hour urine collection without preservative is required.

The volume, dates & times of collection should be noted.

Turnaround Time

1-2 weeks

Sample Stability

Store at 4 ºC for up to seven days, or up to one month at -20 ºC.

Cortisol (Urine)

General Information

Cortisol is the most significant glucocorticosteroid and is essential for the maintenance of several body functions. Like other glucocorticosteroids it is synthesised in the zona fasciculata of the cortex of the Adrenal gland. Cortisol is secreted in response to adrenocorticotrophic hormone (ACTH) which is released from the anterior pituitary gland. Cortisol is bound to cortisol-binding globulin and albumin with only the free (unbound) fraction being biologically active.

Cushing's syndrome is caused by prolonged exposure to elevated levels of either endogenous or exogenous glucocorticoids. Measurement of urinary free cortisol (UFC) in a 24 hour urine collection is frequently used as a first line screening test for Cushing's. It has the advantage in that it is simple for the patient to provide a sample and any increase in cortisol excretion should represent persistant elevation of circulating cortisol. This thereby avoids the problems inherent with interpreting serum cortisol values due to the ACTH-dependent circadian rhythm of cortisol secretion.

Due to problems with incomplete urinary collections and the false positives in UFC which occur in obesity and stressful illness, many clinicians may prefer an overnight or low dose dexamethasone suppression test to UFC measurement.

Patient Preparation

Samples from patients receiving high biotin doses (i.e. >5 mg/day) should be taken at least 8 hours post dose.

Pregnancy, contraceptives and oestrogen therapy give rise to elevated cortisol concentrations.

Samples from patients treated with prednisolone, methyl-prednisolone or prednisone may give falsely elevated concentrations of cortisol.

Notes

None Given

Reference Range

Reference ranges (corrected for 24 hour collection):

<130nmol/24h

Source of Reference Range

Derived in-house

Specifications

  • EQA Scheme?: Yes
  • EQA Status: NEQAS

The laboratories at Heartlands Hospital, Good Hope Hospital and Solihull Hospital form part of the services provided by University Hospitals Birmingham and are UKAS (United Kingdom Accreditation Service) accredited to the ISO 15189:2012 standard. For a list of accredited tests and other information please visit the UKAS website using the following link: https://www.ukas.com/find-an-organisation/

  • Heartlands, Good Hope and Solihull Hospital pathology laboratories are a UKAS accredited medical laboratory No.8217
  • United Kingdom Health Security Agency laboratory is a UKAS accredited medical laboratory No.8213

Tests not appearing on the UKAS Schedule of Accreditation currently remain outside of our scope of accreditation. However, these tests have been validated to the same high standard as accredited tests and are performed by the same trained and competent staff.

For further test information, please visit the test database: http://www.heftpathology.com/frontpage/test-database.html.

For further information contact Louise Fallon, Quality Manager, 0121 424 1235

UKAS HEFT