Dexamethasone suppression test abnormalities in multiple sclerosis: relation to ACTH therapy.

We studied the 1-mg overnight dexamethasone suppression test (DST) in patients with MS. In about 50% of patients, serum cortisol did not fall below 5.0 micrograms/dl. This percentage was similar in patients with major depression, but contrasted to 11% in normal controls. MS nonsuppressors were not more depressed than suppressors; dexamethasone bioavailability may have contributed because nonsuppressors had lower serum dexamethasone levels than suppressors. Suppressors improved in the week following ACTH therapy; nonsuppressors did not. Furthermore, serum dexamethasone values correlated positively with clinical response to ACTH treatment. The DST may be a useful neuroendocrine test of glucocorticoid sensitivity in MS patients.