Cortisol (hydrocortisone) is the major glucocorticoid produced and secreted by the adrenal cortex. It affects the metabolism of protein, fat, and carbohydrates; maintenance of muscle and myocardial integrity; and the suppression of inflammatory and allergic activities.
Normal range:
am cortisol: 8.7 " “22.4 ˇ ¼g/dL
pm cortisol: <10 ˇ ¼g/dL
Use
Discrimination between primary and secondary adrenal insufficiency
Differential diagnosis of Cushing syndrome
Interpretation
The most common cause of increased plasma cortisol levels in women is a high circulating concentration of estrogen (e.g., estrogen therapy, pregnancy), resulting in increased concentration of cortisol-binding globulin.
Patients with severe illness and sepsis have reduced cortisol-binding globulin and albumin levels, resulting in lowered cortisol levels.
Limitations
Bound cortisol circulates in an available but temporarily inactive state. The physiologic activity of cortisol depends on levels of the small fraction of circulating unbound cortisol.
Acute stress (including hospitalization and surgery), alcoholism, depression, and many drugs (e.g., exogenous cortisones, anticonvulsants) can obliterate normal diurnal variation, affect response to suppression/stimulation tests, and cause elevated baseline levels.
Patients taking prednisone may have falsely increased cortisol levels because prednisone is converted to prednisolone after ingestion, and prednisolone has a 41% cross-reactivity.
Cortisol levels may be increased in pregnancy and with exogenous estrogens.
Some patients with depressive disorders have a hyperactive hypothalamic " “pituitary " “adrenal axis, similar to Cushing syndrome.