Cortisol Free
Sample: 24 hrs Urine (Preservative: Boric Ac., 15 g)
Schedule: Daily
Units: nmol/24 hrs
Range: Adults: 70 - 331 nmol/24 hrs. Lower in children because of decreased cortisol production. Values of less than 76 nmol/24 hrs in general excludes Cushings syndrome.
Remarks: Urine Cortisol (Urinary Free Cortisol) is essentially all "free" or unbound fraction. It is the screening test of choise for the diagnosis of Cushings syndrome. This is the most reliable index of cortisol secretion. It is used to evaluate pituitary and adrenal cortical function, especially hyperfunction. Also is used to evaluate hyperglycemia and hypokalemia, to evaluate obese or hypertensive subjects with glucose intolerance, plethora, round face, hirsutism, striae, backache irregular menses.
Urinary Cortisol (Free Urine Cortisol) is a more accurate reflection of cortisol secretion than a single serum cortisol specimen. Urinary cortisol reflects the portion of serum free cortisol (ie, the approx. 6% of serum cortisol not bound to protein) filtered by the kidney. It correlates with cortisol secretion rate. Cushings syndrome is caused by a tumor of pituitary or hyperplasia or tumor of adrenal cortex (See ACTH Suppression and Stimulation tests); ectopic production of ACTH includes that of small cell carcinomas of lung (SCC), carcinoids and medullarythyroid carcinomas.
