What is the role of 24-hour urinary free cortisol (UFC) testing in the diagnosis of McCune-Albright syndrome (MAS)?

Updated: Jan 05, 2021
  • Author: Gabriel I Uwaifo, MD; Chief Editor: George T Griffing, MD  more...
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A 24-hour urinary free cortisol (UFC) is the most sensitive measure of the cortisol production rate and is more accurate in determining Cushing syndrome than random cortisol levels are. Normal values for 24-hour urinary free cortisol vary with the size of the patient and should be adjusted for body surface area to allow comparison with published adult normal ranges (ie, 10-84 µg/1.7 m2/day). Elevated 24-hour urine free cortisol levels suggest Cushing syndrome but do not distinguish between ACTH-dependent and ACTH-independent excess cortisol production.

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