metyrapone stimulation test

Indications

• diagnosis of pituitary Cushing's disease

Contraindications

• DO NOT PERFORM TEST IF PRIMARY ADRENAL INSUFFICIENCY IS LIKELY
• normal response to exogenous ACTH should be demonstrated BEFORE performing test

Reference interval

• standard multiple dose testing
  • serum:
    • 11-deoxycortisol: > 7 ug/dL (202 nmol/L)
    • cortisol: < 3 ug/dL (< 83 nmol/L)
  • 24 hour urine
    • 17-hydroxycorticosteroids: 2-4X base level
    • 17-ketosteroids: > 2X base level
    • 17-ketogenic steroids: 2.5-3 fold rise (> 10 mg/day)
• single dose testing
  • serum:
    • 11-deoxycortisol: > 7 ug/dL (202 nmol/L)
    • cortisol: < 3 ug/dL (< 83 nmol/L)
    • ACTH > 150 pg/mL (> 33 pmol/L)

Clinical significance

• no or impaired response:
  • chemical interferences
    • amitriptyline, chlordiazepoxide, estrogens, glucocorticoids, methysergide, oral contraceptives, phenobarbital, phenothiazines, phenytoin, progestins, rifampin
  • clinical disorders
    • hypopituitarism
      • Cushing's syndrome caused by adrenal tumors or ectopic ACTH-secreting tumors
• Exaggerated response
  • clinical disorders
    • pituitary Cushing's syndrome

Procedure

• standard multiple dose testing
  • collect baseline urine specimen
  • metyrapone 750 mg PO q4h x 6 (children 15 mg/kg)
  • collect serum for 11-deoxycortisol, cortisol at 0800 hours the following morning
  • collect 24 hour urine (multiple dose) for:
    • 17-hydroxycorticosteroids
    • 17-ketosteroids
    • 17-ketogenic steroids
• single dose testing
  • 30 mg/kg PO with milk or snack at midnight
  • collect plasma for 11-deoxycortisol, cortisol & ACTH at 0800 hours the following morning

* To ensure accuracy of 24 hours urine collections & to monitor for adverse effects, the standard test should be done on hospitalized patients. The single-dose test may be done on outpatients.

More general terms

• special chemistry test

Additional terms

• 11-deoxycortisol in serum
• 17-hydroxycorticosteroids in 24 hour urine
• 17-ketogenic steroids in 24 hour urine
• 17-ketosteroids in 24 hour urine
• ACTH (corticotropin) in plasma
• cortisol in serum
• metyrapone (Metopirone)