Overview: Free Cortisol TestIntroduction: The Free Cortisol Test measures free cortisol to diagnose adrenal or pituitary disorders, causing fatigue, weight gain, or muscle weakness. Aligned with 2023 AACE guidelines, it uses an immunoassay for high sensitivity, aiding in endocrine screening. This test is critical for guiding diagnosis, treatment, and improving outcomes in endocrinology for patients with suspected adrenal or pituitary dysfunction.
Other Names: Cortisol Free Assay, Adrenal Function Test.
FDA Status: Laboratory-developed test (LDT), meeting endocrinology standards for diagnostic accuracy.
Historical Milestone: Cortisol testing began in the 1960s with adrenal research. Free cortisol assays emerged in the 1980s, and by the 2000s, high-sensitivity immunoassays improved accuracy.
Purpose: Diagnoses adrenal or pituitary disorders like Cushing's syndrome, guides treatment, and monitors free cortisol levels in patients with fatigue or weight gain.
Test Parameters: 1. Free Cortisol
Pretest Condition: Fasting for 10-12 hours required to stabilize cortisol levels. Collect serum, plasma, or 24-hour urine after overnight fasting. Report symptoms like fatigue or weight gain, and list medications like steroids.
Specimen: 2-5 mL serum (SST), 2-4 mL plasma (EDTA), or 50-100 mL 24-hour urine (sterile container). Centrifuge serum/plasma within 1 hour. Transport in a biohazard bag within 8 hours.
Sample Stability at Room Temperature: 8 hours
Sample Stability at Refrigeration: 7 days
Sample Stability at Frozen: 6 months
Medical History: Document fatigue, weight gain, or history of adrenal/pituitary disorders. Include current medications, especially steroids or hormone therapies.
Consent: Written consent required, detailing the tests purpose, diagnostic implications, and potential need for adrenal or pituitary therapy.
Procedural Considerations: Uses an immunoassay to measure free cortisol levels. Results are available in 3-5 days, supporting clinical decisions.
Factors Affecting Result Accuracy: Non-fasting samples, stress, or steroids may alter results. Improper storage can degrade samples.
Clinical Significance: Elevated free cortisol levels indicate Cushing's syndrome, prompting therapy. Low levels suggest adrenal insufficiency, requiring supplementation.
Specialist Consultation: Consult an endocrinologist for result interpretation. A neurosurgeon referral is advised for pituitary-related cases.
Additional Supporting Tests: ACTH test, dexamethasone suppression test, or adrenal imaging to confirm adrenal or pituitary disorders.
Test Limitations: Results may be affected by stress or medications. Clinical correlation is required.
References: AACE Cushing's Guidelines, 2023; Journal of Clinical Endocrinology, Nieman LK, 2022.
