Austin Pathology

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Cortisol - Serum

Ordering Information
Significant diurnal variation occurs in the circulating cortisol concentration, so a single blood sample is of limited value. Peak values occur between 0800 - 1000hrs, and trough values occur in the late afternoon and evening. 
Laboratory
Biochemistry
Specimen
Blood
Container
Serum tube (gold top)
Additional Collection Instructions
Can combine with other Chemistry tests requiring same tube type.
Minimum Adult Volume
5mL
Minimum Paediatric Volume
1mL
Frequency
Daily
Reference Interval

 

CORTISOL 6:00 to 10:00 (AM) ALL 185 - 624 nmol/L
CORTISOL 16:00 to 20:00 (PM) ALL <276 nmol/L

 Source: Beckman-Coulter.

 

For the Beckman cortisol assay, the minimum peak cortisol cut-off (2.5th centile) for healthy subjects 30 mins post IV Synacthen is:

Males and Females (not on OCP): 460 nmol/L

Females on OCP: 600 nmol/L

Source: ESA/AACB/RCPA HEDT Guideline.