title: The influence of oral contraceptives on overnight 1 mg dexamethasone suppression test.
abstract: BACKGROUND
  In suspected hypercortisolism, the 1 mg dexamethasone suppression test is the usual initial test. In fertile women, false-positive test results are often due to the use of oral contraceptives. By elevating cortisol-binding globulin these contraceptives increase the total serum cortisol concentration. The aim of this study was to assess the duration and degree of influence of oral contraceptives on the low-dose dexamethasone suppression test.
  
  
  METHODS
  Thirteen healthy female volunteers without symptoms or signs of overt hypercortisolism, aged 18-55 years, who were using oral contraceptives, underwent a 1 mg dexamethasone suppression test. Tests were repeated one and six weeks after withdrawal of the contraceptive. In addition, 24-hour urinary cortisol excretion and late-night salivary cortisol were measured.
  
  
  RESULTS
  Of the 13 volunteers (62%) eight had inadequate suppression of cortisol by 1 mg dexamethasone while using oral contraceptives. One week after the contraceptive was withdrawn, the number of false-positive results significantly decreased to 1 (8%, p < 0.02). Six weeks after discontinuation, all tests were normal. None of the 24-hour urinary cortisol samples and just one late-night salivary cortisol level was elevated.
  
  
  CONCLUSIONS
  The results of the 1 mg dexamethasone suppression test performed one week after cessation of oral contraceptives are accurate in almost all subjects. In case of inadequate suppression, a second test may be performed after six weeks. In this manner the 1 mg dexamethasone suppression test can reliably be done at the end of a seven-day break from contraceptive use in nearly all cases.
authors.affiliation: Department of Internal Oncology, Erasmus MC, Rotterdam, the Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Vastbinder
authors.forename: M
authors.initials: M
authors.lastname: Kuindersma
authors.forename: A H
authors.initials: AH
authors.lastname: Mulder
authors.forename: M P
authors.initials: MP
authors.lastname: Schuijt
authors.forename: A H
authors.initials: AH
authors.lastname: Mudde
mesh_terms: D000293:Adolescent; D000328:Adult; D003276:Contraceptives, Oral / Q000008:administration & dosage / Q000009:adverse effects; D003480:Cushing Syndrome / Q000097:blood / Q000175:diagnosis*; D003907:Dexamethasone / Q000008:administration & dosage* / Q000097:blood / Q000652:urine; D004347:Drug Interactions; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage* / Q000097:blood / Q000652:urine; D006801:Humans; D006854:Hydrocortisone / Q000097:blood* / Q000652:urine*; D007118:Immunoassay; D008875:Middle Aged; D012463:Saliva / Q000378:metabolism; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D003276:Contraceptives, Oral; D005938:Glucocorticoids; D003907:Dexamethasone; D006854:Hydrocortisone