PLASMA DEXAMETHASONE CONCENTRATIONS AND DIFFERENTIAL SUPPRESSION RESPONSE OF CORTISOL AND CORTICOSTERONE IN DEPRESSIVES AND CONTROLS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 19  (3) , 281-291
Abstract
After a dexamethasone suppression test (DST), cortisol, corticosterone and the test substance were determined by a direct radioimmunoassay in 42 samples obtained from 22 depressed patients and 8 controls. The DST results of both glucocorticoids agreed in most of the tests. In all 7 cases with elevated but not definitely abnormal post-DST (1600 h) cortisol levels (transitional range 30 to 50 ng/ml) the concurrent determination of corticosterone indicated that this corticosteroid may serve as a potent additional discriminator. Dexamethasone plasma concentrations at 1600 h after a 1-mg test dose of dexamethasone at 2300 h were significantly (P < 0.01) lower in cortisol and corticosterone nonsuppressors than in suppressors. Since these data were obtained 17 h after ingestion of dexamethasone (half-life 3.5 to 5 h ) any conclusions about an inverse correlation between dexamethasone and corticosteroid plasma concentrations would be speculative. The dexamethasone pharmacokinetics might be an important variable and may contribute to some of the recent uncertainty about the DST.