Cortisol Is Secreted Episodically in Cushing's Syndrome1

It has recently been demonstrated that the total daily production of cortisol by normal man is accomplished in a series of discontinuous secretory episodes (Fig 1) separated by periods of quiescence of the adrenal cortex (1). In the normal it was shown that the adrenals did not secrete cortisol for about 18 hours of each day. The proof was based upon measurement of the specific activity of plasma cortisol in association with rises and falls in the plasma cortisol concentration measured at brief intervals. Rises in plasma level were accompanied by drops in cortisol specific activities while falls were associated with unchanged specific activity. It was also demonstrated that this episodic secretory activity persisted throughout the 24 hour sleep-awake cycle. It was of considerable importance to establish whether a similar pattern of secretion existed in Cushing's syndrome due to bilateral adrenal hyperplasia. It has been possible to study a carefully selected patient and to resolve the problem with the finding that cortisol is secreted episodically in Cushing's syndrome in a pattern remarkably similar to the normal except for the greater total quantity of cortisol introduced.