Cortisol is a steroid hormone produced by the adrenal glands, regulated by the hypothalamic-pituitary-adrenal (HPA) axis.

Levels normally follow a diurnal rhythm (highest in the morning, lowest at night).

A random cortisol test provides a snapshot of cortisol concentration at the time of sampling.

Clinical uses include:

Screening for adrenal insufficiency (Addison’s disease).

Supporting diagnosis of Cushing’s syndrome (excess cortisol).

Evaluating stress response and certain endocrine disorders.

Monitoring patients on steroid therapy.

Often combined with ACTH stimulation test or dexamethasone suppression test for more definitive diagnosis.

Analyte: Serum cortisol concentration (µg/dL).

Normal Range (varies by lab):

Morning (8 AM): 5 – 25 µg/dL

Afternoon/Evening: Lower values expected

Abnormal Findings:

Low cortisol: Suggests adrenal insufficiency, pituitary dysfunction, or suppression due to steroid therapy.

High cortisol: Indicates possible Cushing’s syndrome, stress, or adrenal hyperfunction.

Clinical Use:

Provides a quick assessment of adrenal function.

Helps differentiate causes of fatigue, weight changes, and abnormal blood pressure.

Guides further endocrine testing and treatment decisions.