CORTISOL, RANDOM

The Cortisol, Random test measures the concentration of cortisol in a blood sample collected at the time requested by the treating doctor. Cortisol is a steroid hormone produced by the adrenal glands, which are located above the kidneys. Its production is controlled by a coordinated pathway involving the hypothalamus, pituitary gland and adrenal glands, commonly called the hypothalamic-pituitary-adrenal or HPA axis.

Cortisol supports the body's response to physical and emotional stress, helps regulate blood glucose and blood pressure, influences metabolism and contributes to immune and inflammatory control. Cortisol production follows a circadian rhythm. Levels are generally highest in the early morning after waking and progressively decline through the day, reaching their lowest point around late evening or midnight.

Because cortisol varies according to the time of day, sleep pattern, stress, illness and medicine use, a random cortisol result must be interpreted using the exact sample-collection time and clinical situation. A result collected at an unspecified time should not be interpreted using a fixed morning cortisol reference interval.

Benefits of the Test

A random cortisol measurement provides information about the patient's cortisol concentration at a particular moment. It may be useful in selected clinical circumstances, especially when a doctor needs an immediate measurement during an acute illness or when the sample is being interpreted with symptoms, treatment history and other hormone tests.

• Measures serum cortisol at the documented collection time.
• Provides information about adrenal hormone production.
• May support the initial assessment of suspected adrenal insufficiency.
• May assist in evaluating unexplained weakness or low blood pressure.
• Can be used in selected acute or hospital-based clinical assessments.
• May be interpreted with ACTH to assess the HPA axis.
• Can help monitor selected patients receiving corticosteroid treatment.
• May contribute to further endocrine investigation when interpreted by a specialist.
• Requires only a routine venous blood sample.
• Usually provides a same-day or next-day report.

A random cortisol value has important limitations. Cortisol is released in pulses and changes throughout the day, so one measurement may not accurately represent average production or adrenal reserve. A morning cortisol, ACTH stimulation test, dexamethasone suppression test, late-night salivary cortisol or 24-hour urinary free cortisol may be more appropriate for particular clinical questions.

Why Doctors Recommend This Test

A doctor may request random cortisol when adrenal insufficiency is considered in a patient who is acutely unwell or has symptoms compatible with insufficient cortisol. Possible symptoms include persistent fatigue, muscle weakness, loss of appetite, unexplained weight loss, nausea, vomiting, abdominal discomfort, dizziness, low blood pressure, salt craving or episodes of low blood glucose.

Primary adrenal insufficiency, also called Addison disease, occurs when the adrenal glands cannot produce adequate cortisol. Secondary or tertiary adrenal insufficiency may result from pituitary or hypothalamic disorders or suppression of the HPA axis following prolonged corticosteroid treatment.

The test may also be requested when a patient has features suggesting excessive cortisol production, such as central weight gain, easy bruising, purple stretch marks, muscle weakness, high blood pressure, high blood glucose, osteoporosis or menstrual changes. However, a random serum cortisol test is not considered an adequate stand-alone screening test for Cushing syndrome.

Doctors commonly use an overnight dexamethasone suppression test, late-night salivary cortisol or 24-hour urinary free cortisol when evaluating suspected endogenous Cushing syndrome. The selection of the correct test depends on symptoms, medicine use and specialist assessment.

In hospitalised or critically ill patients, cortisol may be measured as part of an urgent evaluation. Severe infection, trauma, surgery, pain and other acute stresses can significantly increase cortisol. Results obtained during acute illness cannot always be compared directly with values from healthy individuals.

Preparation Before Test

The patient should follow the instructions provided by the referring doctor or Focus Diagnostics. Random cortisol testing does not always require fasting, but fasting may be necessary when other blood tests are ordered simultaneously.

• Confirm the required collection time with the doctor or laboratory.
• Inform the laboratory of the exact time the sample is collected.
• Tell the doctor about all steroid tablets, injections, inhalers, creams and nasal sprays.
• Report medicines such as hydrocortisone, prednisolone, prednisone and dexamethasone.
• Do not stop corticosteroids suddenly without medical supervision.
• Tell the laboratory about oral contraceptives, oestrogen therapy and pregnancy.
• Inform the doctor about anticonvulsants and other long-term medicines.
• Report high-dose biotin or hair-and-nail supplements.
• Avoid unusually strenuous exercise before collection unless otherwise instructed.
• Inform the staff about acute illness, recent surgery, trauma or severe stress.

Stopping corticosteroids abruptly can be dangerous, particularly after prolonged use, because the body's natural cortisol production may be suppressed. Any change in dose or timing must be directed by the treating doctor.

Sample Collection Procedure

A trained phlebotomist collects a blood sample from a vein, usually in the arm. The skin is cleaned, a sterile needle is inserted and blood is collected into an appropriate tube. The procedure usually takes only a few minutes.

The collection time should be recorded because cortisol reference intervals and clinical meaning vary throughout the day. Relevant information such as current steroid treatment, recent dexamethasone, hydrocortisone administration, pregnancy or oral contraceptive use should also be available to the interpreting doctor.

The sample is processed in the laboratory and cortisol is commonly measured using an immunoassay or another validated analytical method. Results obtained using different laboratory methods may not be directly interchangeable.

Normal Reporting Time

The Random Cortisol test is generally reported on the same working day or within 24 hours after the laboratory receives an acceptable sample. The exact turnaround time can vary according to collection location, transportation, laboratory workload, instrument availability, quality-control verification or the need for repeat analysis.

When adrenal crisis is suspected, testing and treatment require urgent hospital-based medical management. Treatment should not be delayed solely while waiting for a routine laboratory report when the patient's clinical condition requires immediate intervention.

Who Should Take This Test?

A random cortisol test may be considered for selected patients following medical evaluation. The doctor should determine whether a random sample, timed morning sample or dynamic endocrine test is most appropriate.

• Patients being evaluated for possible adrenal insufficiency.
• People with unexplained persistent weakness or severe fatigue.
• Patients with low blood pressure, dizziness or fainting.
• People with unexplained low sodium or high potassium.
• Patients with recurrent low blood glucose.
• People who have used corticosteroids for a prolonged period.
• Patients who recently stopped or reduced steroid treatment.
• People with pituitary or hypothalamic disorders.
• Selected acutely ill or hospitalised patients.
• Patients undergoing endocrine evaluation under specialist guidance.

The test should not be used by itself to diagnose Addison disease, adrenal insufficiency or Cushing syndrome. Additional testing is often required.

Understanding the Results

The result may be reported in micrograms per decilitre or nanomoles per litre. Interpretation depends on the time of sample collection, laboratory method and clinical context. Patients should use the reference interval printed on the Focus Diagnostics report.

A morning cortisol value cannot be interpreted in the same way as an afternoon or evening result. Cortisol is naturally higher in the early morning and lower later in the day. Shift work, disrupted sleep and acute illness may alter this normal rhythm.

A low cortisol result may be seen in primary adrenal insufficiency, pituitary disease, hypothalamic disease or suppression caused by prolonged corticosteroid use. However, a single random low result does not establish the diagnosis. A properly timed morning cortisol, ACTH measurement and ACTH stimulation test may be required.

A high cortisol result can occur with acute stress, severe illness, pain, trauma, surgery, pregnancy, oestrogen treatment, depression, alcohol-related illness or endogenous cortisol excess. A random high value does not independently diagnose Cushing syndrome.

Primary and Secondary Adrenal Insufficiency

In primary adrenal insufficiency, the adrenal glands are unable to produce enough cortisol. ACTH commonly rises because the pituitary gland attempts to stimulate the adrenal glands. Patients may also have low aldosterone, low sodium, high potassium, low blood pressure and increased skin pigmentation.

In secondary adrenal insufficiency, inadequate ACTH production from the pituitary gland leads to reduced cortisol. Both ACTH and cortisol may be low or inappropriately normal. Potassium may remain normal because aldosterone regulation is often preserved.

Doctors may request ACTH with cortisol and perform a short ACTH or cosyntropin stimulation test. During the stimulation test, cortisol is measured before and after synthetic ACTH administration to evaluate adrenal response.

Cortisol and Cushing Syndrome

Cushing syndrome occurs when the body is exposed to excessive cortisol for a prolonged period. The most common overall cause is corticosteroid medication. Endogenous Cushing syndrome can result from excess ACTH or cortisol production within the body.

Random serum cortisol is affected by normal daily variation and stress and therefore is not an appropriate stand-alone test to confirm or exclude Cushing syndrome. More suitable initial investigations may include late-night salivary cortisol, 24-hour urinary free cortisol or an overnight dexamethasone suppression test.

Factors That Can Affect the Results

• The exact time of sample collection.
• Normal circadian rhythm and sleep schedule.
• Acute physical or emotional stress.
• Hospitalisation, surgery, infection, pain or trauma.
• Pregnancy and oestrogen-containing medicines.
• Corticosteroid tablets, injections, inhalers, creams or nasal sprays.
• Certain anticonvulsants and other medicines.
• Depression and significant alcohol use.
• High-dose biotin supplementation.
• Differences in laboratory analytical methods.

Oestrogen can increase cortisol-binding globulin, which may raise total serum cortisol without a corresponding increase in biologically active free cortisol. Kidney or liver disease can also influence cortisol-binding proteins and complicate interpretation.

Detailed Information

The hypothalamus releases corticotropin-releasing hormone, which stimulates the pituitary gland to release ACTH. ACTH then stimulates the adrenal cortex to produce cortisol. Cortisol feeds back to the hypothalamus and pituitary gland to help regulate further hormone release.

Healthy cortisol secretion is both pulsatile and circadian. A random test captures only one point within this changing pattern. This is why the result may suggest the need for further investigation but frequently cannot provide a final endocrine diagnosis by itself.

Patients should discuss the result with the referring doctor or endocrinologist. Additional investigations may include 8–9 AM cortisol, plasma ACTH, serum electrolytes, glucose, renin, aldosterone, ACTH stimulation testing, dexamethasone suppression testing, late-night salivary cortisol or 24-hour urinary free cortisol.

Severe weakness, persistent vomiting, abdominal pain, very low blood pressure, confusion, dehydration, fainting or reduced consciousness may indicate an adrenal crisis. This is a medical emergency requiring immediate hospital treatment.