Plasma 3,4-dihydroxyphenylethyleneglycol levels in depressed patients with and without abnormal dexamethasone suppression.

Escape from dexamethasone-induced suppression of plasma cortisol is an abnormality found in about half of patients with major depression. It has been hypothesized that this hyperactivity of the hypothalamo-pituitary-adrenal axis might be related to a central noradrenergic hypofunction. The present study was designed to test this hypothesis by measuring plasma 3,4-dihydroxyphenylethyleneglycol (DOPEG) levels (free and conjugated forms), an index of central noradrenergic activity, and by simultaneously carrying out a dexamethasone suppression test. Forty-five patients with a diagnosis of major depression (according to the DSM-III) were investigated. Plasma DOPEG levels (measured at 8 a.m.) were found to be similar in dexamethasone suppressor and nonsuppressor depressed patients. These results do not support the hypothesis that central noradrenergic hypoactivity underlies nonsuppression of dexamethasone in major depression.