hypothalamus -------> CRH (corticotropin-releasing hormone)-------> pituitary----->ACTH (adrenocorticotrophin hormone)-----> adrenal cortex----->cortisol

 Diurnal variation- The production of cortisol varies throughout a 24-hour period, highest in the early morning at around 6-8 am and are lowest around midnight for normal healthy people. The normal range is 6-23 mcg/dl. It is higher after meals.

Cortisol levels can be measured through blood, urine (by measuring 24 hr urine sample for 17-KS or 17-OHCS) or saliva.