Diagnostic Performance of Screening Tests for Cushing s Syndrome
Condition: Cushing's Syndrome
MeSH terms: Cushing Syndrome; Syndrome
Study type: Observational

Summary: 
      This study will test the accuracy of screening tests for Cushing s syndrome in overweight
      people with signs of the disorder. Cushing s syndrome is a rare disorder caused by excess
      production of the hormone cortisol. Patients may have various problems, such as weight gain,
      high blood pressure, diabetes, infections, mood problems, trouble concentrating, and
      increased blood clotting. These symptoms are seen in many other disorders as well,
      complicating the diagnosis. The reliability of tests currently used to diagnose Cushing s
      syndrome is not known. To test their accuracy, subjects in this study who test positive for
      Cushing s syndrome will be evaluated at NIH for 2 years to either confirm or refute the
      laboratory results.

      Patients between 18 and 75 years of age who are being treated at the George Washington
      University Weight Management Program (GWUWMP) may participate in this study. Candidates will
      be screened with a medical history, physical examination, measurement of body fat, blood
      tests, and oral glucose tolerance test. They will also complete a symptoms checklist and
      quality of life questionnaire.

      Participants will be tested for Cushing s syndrome with a saliva collection, 24-hour urine
      collection, and dexamethasone suppression test (DST). For the DST they will take 1 mg of
      dexamethasone at night and report to GWUWMP the next morning for a blood draw. All specimens
      blood, saliva, and urine will be tested for cortisol levels.

      People whose test results are abnormal will be seen at the NIH outpatient clinic for a
      medical history, physical examination, and blood tests; bedtime saliva collection; two
      24-hour urine collections; and a 2-day 2-mg DST, followed by administration of
      corticotropin-releasing hormone (CRH). CRH is a naturally occurring hormone that causes
      cortisol levels to rise. Pre-treatment with dexamethasone prevents CRH from causing an
      increase in cortisol in healthy people, but not in patients with Cushing s syndrome. For the
      2-day DST, the subject takes 0.5 mg dexamethasone every 6 hours for eight doses. Two hours
      after the last dose, CRH is injected through a catheter (thin plastic tube) inserted into an
      arm vein. Blood is drawn just before giving CRH to measure dexamethasone and cortisol levels
      and after giving CRH to measure cortisol levels.

      People whose test results are normal will not be seen further at NIH. Those with high
      cortisol levels will have repeat urine and saliva tests every 2 to 8 weeks for up to 24
      months, and a 1-mg DST every 3 months during routine clinic visits at GWUWMP. People whose
      increased cortisol is found to be due to another condition besides Cushing s syndrome will be
      referred for evaluation and possible treatment. Those diagnosed with Cushing s syndrome will
      have standard tests to identify the tumor causing the disorder, followed by standard medical
      and surgical treatment.
    

Detailed description: 
      Cushing's syndrome is a rare disorder characterized by a variety of clinical signs and
      symptoms that reflect chronic exposure to hypercortisolism such as obesity, hypertension,
      glucose intolerance, infections, psychiatric disturbance, impaired cognition and
      hypercoagulability. Thus, it is important to screen for this treatable disorder so as to
      prevent its associated morbidity and mortality. Because many of the signs of Cushing's
      syndrome are common in the general population, information about the cost-effectiveness and
      diagnostic efficiency of various screening tests would be useful.

      This study will evaluate the diagnostic performance of various screening tests for Cushing's
      syndrome in overweight patients recruited from a weight loss center who have additional signs
      of the disorder. Patients with abnormal tests will be seen as outpatients at the NIH for
      further evaluation for up to two years to confirm or refute the possibility that they have
      Cushing's syndrome. Patients with the disorder will be treated.
    

Observational model: Cohort
Time perspective: Prospective
Keywords: Dexamethasone; Cushing Syndrome