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Dr. D. Love
Dr. D. Love, Doctor
Category: Endocrinology
Satisfied Customers: 17547
Experience:  Family Physician for 10 years; Hospital Medical Director for 10 years.
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Now I calculate urine cortisol/creatinine ratio of my

Customer Question

Hello.Now I calculate urine cortisol/creatinine ratio of my patients, but I can't figure how to calculate. So I need someone's help to teach me about urine cortisol/creatinine ratio. Urine volume 1100ml/12hrscortisol, urine: 105ug/12hrscreatinine, urine: 1g/12hrsThe reason that I can't finish 24hr urine collection is my patient's schedule. She has to discharge today, so I have end up urine collection at 12hrs.
JA: Thanks. Can you give me any more details about your issue?
Customer: My patient is already diagnosed in Pituitary cushing's syndrome, but she doesn't take any pill.
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Submitted: 9 months ago.
Category: Endocrinology
Expert:  Dr. D. Love replied 9 months ago.

Hello from JustAnswer.

The use of a urine cortisol / creatinine ratio is typically done on a single urine sample, rather than a timed urine collection. This is done to compensate for the amount of dilution of the urine. On the other hand, when a timed urine collection is done, the usual measurement is of total free cortisol. With a timed urine collection and calculation of the total cortisol, the amount of dilution does not matter. A timed urine collection is usually done over 24 hours to account for the significant diurnal variation in cortisol levels, so a 12 hour collection cannot simply be doubled.

The current guidelines for diagnosis of Cushing syndrome recommends the use of a 24 hour urine free cortisol, rather than a cortisol/creatinine ratio.

However, when a single urine sample is used to determine the cortisol / creatinine ratio, the concentration of each result is simply divided. So the ratio = concentration of cortisol / concentration of creatinine. See http://www.ncbi.nlm.nih.gov/pubmed/23565435.

If I can provide any additional information, please let me know.

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