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CORTISOL ASSAYS

BIOCHEMISTRY

mprasadnaidu
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CORTISOL ASSAYS

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  1. CORTISOL ASSAYS 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. Urine free cortisol assay • RIA • Immunoassays • Liquid chromatography Disadvantages Pretreatment of urine sample

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

  10. THANK YOU

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