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Immediate and Delayed Alterations of Adrenocorticotropin and Cortisol Nyctohemeral Profiles after Corticotropin-Releasing Factor in Normal Man^*

Free University of Brussels Brussels, Belgium

Address all correspondence and requests for reprints to: Dr. G. Copinschi, Laboratory of Experimental Medicine, University of Brussels, rue Evers 2, B-1000 Brussels, Belgium.

Intravenous injections of 50 µg corticotropinreleasing factor (CRF) to four normal men at 0900 and 2300 h were followed by significant plasma ACTH and cortisol elevations, without changes in GH and PRL concentrations. The responses were more easily assessed late in the evening than in the morning, when they were superimposed upon the spontaneous hormonal variations. The initial hormonal response was always followed by a period of decreased hormonal values compared to control patterns. The normal pituitary-adrenal response to CRF was blunted or abolished by prior administration of dexamethasone. These data suggest that exogenous administration or CRF-induced endogenous production of glucocorticoids modulates the sensitivity of corticotropic cells to the action of CRF. Since normal ACTH and cortisol secretory episodes are likely to obscure the effects of CRF, stimulation tests for clinical purposes should be performed during the quiescent period, i.e. late in the evening.

^* This work was supported in part by the Belgian FRSM, SABENA (Belgian World Airlines), APMO Foundation, and the Belgian Division of Pfizer Laboratories. It was performed in part under contract of the Ministere Beige de la Politique Scientifique (actions concertées).

Received May 23, 1983.

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