Evaluation of the three hour metyrapone test in adults

The prolonged metyrapone test is used to assess the hypothalamic-pituitary-adrenal axis. The dynamic responses of cortisol, ACTH and 11-deoxycortisol over the 3 h of the single morning dose metyrapone test have been examined in fourteen normal adult subjects. In every case there was a rapid, sustained fall in cortisol, but the resultant ACTH responses were extremely variable and in two subjects did not exceed values obtained during the control studies. The rise in 11-deoxycortisol was also variable and in several instances occurred without any significant elevation in ACTH. In these cases, the rise in 11-deoxycortisol may be due to a normal level of production of steroids with a shift from cortisol to 1-deoxycortisol induced by the metyrapone. Thus, the hypothalamic-pituitary-adrenal axis may not be adequately tested, and this together with the high incidence of unpleasant side effects, makes the 3 h oral metyrapone test unsatisfactory for routine use in adults.