Cortisol Assay, 3 Samples: PRE (Baseline) and 2 POST Dexamethasone Suppression
Specimen
PRE: 0.5 mL serum in red top, white top, or serum separator tube for baseline sample (labeled PRE); each POST: 0.5 mL serum in red top, white top, or serum separator tube for each post sample (labeled POST)
Test Description
This test measures cortisol concentrations before and after administration of exogenous dexamethasone. This suppression test requires three samples; baseline cortisol prior to dexamethasone administration and two cortisol levels post dexamethasone administration (4 and 8 hours). The low-dose dexamethasone suppression test is preferred for diagnosing hyperadrenocorticism. The high-dose dexamethasone suppression test is used to differentiate pituitary-dependent from adrenal tumor hyperadrenocorticism.