Serum cortisol – laboratory test

Opis produktu

Why cortisol is tested

Cortisol is a hormone produced by the adrenal cortex, known as the stress hormone. It regulates glucose, blood pressure, the stress response and inflammation. Its secretion follows a daily rhythm: it peaks between 6:00 and 8:00 in the morning and reaches its lowest level around midnight. Serum testing is used to detect deficiency (adrenal insufficiency, Addison’s disease, pituitary damage) and excess (Cushing’s syndrome), and to monitor patients receiving glucocorticoids.

When to consider this test

• persistent weakness, weight loss, low blood pressure, dizziness on standing, darkening of the skin or salt cravings (suspected adrenal insufficiency),
• weight gain around the trunk, a rounded face, stretch marks, high blood pressure, diabetes, osteoporosis or easy bruising (suspected Cushing’s syndrome),
• after long-term steroid treatment, particularly following abrupt withdrawal,
• in pituitary disease, after head injuries or with unexplained hyponatraemia.

How to prepare

• Have the sample collected in the morning between 7:00 and 9:00, unless your doctor specifies another time. Record the exact collection time; without it, the result cannot be interpreted.
• Fast for 8–12 hours, drinking only water in the morning. Attend after a good night’s sleep, avoid exercise the day before and avoid alcohol for 48 hours.
• Sit and rest for 15–20 minutes before sample collection. Do not smoke in the morning.
• Tell your doctor about steroids (including inhalers, creams and joint injections), contraception and oestrogens: they raise or otherwise affect the result. Prednisone cross-reacts in the assay and produces a falsely high cortisol result.

Understanding your result

Results are reported in µg/dl or nmol/l (1 µg/dl = 27,6 nmol/l). The reference range depends on the collection time and method; compare your result with the range on the report. As a guide (Mayo Clinic Laboratories, adults):

A high morning result does not establish a diagnosis of Cushing’s syndrome; the most common causes are stress, depression, obesity, alcohol, pregnancy and oestrogens. A low morning result accompanied by symptoms requires urgent investigation, as adrenal insufficiency can progress to an adrenal crisis.

Other tests to consider alongside cortisol

The doctor usually also requests ACTH, sodium and potassium, glucose, DHEA-S, and, if excess is suspected, 24-hour urinary cortisol or salivary cortisol. Read more about the adrenal glands and stress: Badania-Medyczne.pl.

Sources: ALAB laboratoria, Cortisol (preparation, daily rhythm, indications); Mayo Clinic Laboratories, Cortisol, Serum (morning/afternoon reference ranges, interference: prednisone, oestrogens, stress). For information only; does not replace medical advice.