MSc Medical Biochemistry, Ph.D,.
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.
Cortisol is a glucocorticoid hormone secreted by the
zona fasciculata of adrenal cortex.
Cortisone & corticosterone are the other
CRH(corticotropin releasing hormone)
&ACTH(adrenocorticotrophic hormone) stimulate
These steroid hormones act through intracellular
messengers & increase the rate of transcription.
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.
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.
This steroid plays pivotal role in
Maintenance of electrolyte balance & blood
Immune modulation & stress response,
Cell proliferation & differentiation,
Memory & cognitive functions