Cortisol is a steroid hormone regulated by ACTH from the pituitary gland.

It plays a vital role in metabolism, immune response, and stress regulation.

Cortisol levels follow a diurnal rhythm: highest in the morning and lowest at night.

Clinical uses include:

Diagnosing adrenal insufficiency (Addison’s disease).

Detecting Cushing’s syndrome (excess cortisol production).

Evaluating pituitary or adrenal gland disorders.

Monitoring patients on long‑term steroid therapy.

Often performed alongside ACTH stimulation test, dexamethasone suppression test, and 24‑hour urinary cortisol for comprehensive evaluation.

Analyte: Serum Cortisol (µg/dL).

Normal Range (varies by lab and time of day):

Morning (6–8 AM): ~5–25 µg/dL

Evening (6–8 PM): ~2–9 µg/dL

Abnormal Findings:

High cortisol: Cushing’s syndrome, stress, adrenal hyperplasia, pituitary adenoma.

Low cortisol: Addison’s disease, adrenal insufficiency, pituitary dysfunction.

Clinical Use:

Provides a marker of adrenal gland function and stress response.

Helps guide diagnosis and monitoring of endocrine disorders.

Supports critical care and metabolic evaluations.