The relationship of the A.M. and P.M. readings are used to determine adrenal response to stress

• Use Establish the diagnosis of adrenocortical insufficiency, Addison's disease, adrenocortical hypersecretion, Cushing's syndrome. Malfunction of the organs in the hypothalamic - pituitary - adrenal cortex axis will result in alteration of the cortisol levels. First among adrenal function tests for most needs. Elevated levels are found in the newborn period.
• Methodology Immunochemiluminometric assay (ICMA).
• Additional Information Cortisol is the major adrenal glucocorticoid steroid hormone, and is normally under feedback control by pituitary ACTH and the hypothalamus.
• Causes of low cortisol include pituitary destruction or failure, with resultant loss of ACTH to stimulate the adrenal and metabolic errors or destruction of the adrenal gland itself (adrenogenital syndromes, tuberculosis, histoplasmosis). The diagnosis of hypoadrenalism generally requires confirmation with ACTH stimulation, due to the circadian rhythms of cortisol and other factors. Causes of increased cortisol, may be loss of normal diurnal variation, include pituitary overproduction of ACTH, production of ACTH by a tumor (notably oat cell cancers), and adrenal adenomas.
• Cortisol A.M. normal range is 5 -25 µg/dL.
• Cortisol P.M. normal range is approx. 2.5 - 12.5 µg/dL.
• Values obtained with different assay methods should not be used interchangeably.