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1. M.Prasad Naidu
MSc Medical Biochemistry, Ph.D,.

2. Introduction
 Cortisol level measurement is used in the assessment of
adrenal,pituitary & hypothalamic function & is
especially important in the diagnosis of Cushing’s
syndrome & Addison’s disease.
 Total serum cortisol,24 hr urinary free cortisol,salivary
free cortisol are measured.

5. Physiology
 Cortisol is a glucocorticoid hormone secreted by the
zona fasciculata of adrenal cortex.
 Cortisone & corticosterone are the other
glucocorticoids.
 CRH(corticotropin releasing hormone)
&ACTH(adrenocorticotrophic hormone) stimulate
cortical secretion.
 These steroid hormones act through intracellular
messengers & increase the rate of transcription.

9. Contd-------
 70% of cortisol in blood is bound to
CBG(cortisol binding globulin).
 20% bound to albumin.
 The rest is free, which is biologically active.
 Metabolism takes place in liver.
 These are first reduced & excreted as their
glucuronides or sulphates in urine.

10. Contd
 Cortisol levels in blood are characterised by
Circadian rhythm with a morning maximum,
 Declining levels throughout the daytime
 A period of low concentration around midnight
& rise after the first few hours of sleep
 This circadian rhythm has been demonstrated
in plasma,than in urine & saliva.

11. Functions
This steroid plays pivotal role in
 Energy metabolism
 Maintenance of electrolyte balance & blood
pressure,
 Immune modulation & stress response,
 Cell proliferation & differentiation,
 Memory & cognitive functions

13. Laboratory cortisol assays
Serum total cortisol
 Radioimmunoassay
 Liquid chromatography
 HPLC
 Fluorescence polarisation immunoassay
Serum free cortisol assays
 Coolen’s method
 Ultrafiltration
Disadvantages
 Invasive procedure
 Stress induced rise of cortisol level

14. Urine free cortisol assay
 RIA
 Immunoassays
 Liquid chromatography
Disadvantages
Pretreatment of urine sample

15. Salivary cortisol assays
RIA
Immunoassays
Liquid chromatography
Advantages
Noninvasive procedure