Recovery of Hypothalamic-Pituitary-Adrenal Function, Growth Hormone Responsiveness and Sleep EEG Pattern in a Patient Following Removal of an Adrenal Cortical Adenoma

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Abstract
A patient with Cushing's syndrome secondary to an adrenal cortical adenoma exhibited low plasma ACTH levels, diminished adrenal responsiveness to ACTH, absence of circadian periodicity of plasma ACTH and cortisol levels, absence of plasma ACTH, cortisol and growth hormone response to hypoglycemia or Pitressin® administration and absence of the nocturnal elevation of plasma growth hormone levels. EEG sleep stages III and IV were absent and there was an increase in the percentage of Stage I sleep and a reduction in REM periods. Repeat studies were performed 3¾12, 7, 12 and 16 months postoperatively. Return of normal adrenal responsiveness to ACTH, normal basal plasma ACTH and growth hormone levels, and normal plasma ACTH, cortisol and growth hormone responses to Pitressin® and hypoglycemia were noted in the study 3¾12 months postoperatively. Circadian periodicity of plasma ACTH and cortisol levels and nocturnal elevation of plasma growth hormone levels was not evident until 7 months postoperatively. The sleep EEG pattern did not become normal until 16 months postoperatively. These studies reveal a different time pattern of return of “stress” induced and circadian ACTH release, and support the suggestion of the existence of different control mechanisms for these parameters. They also indicate a dissociation between the factors involved in slow wave sleep (SWS-Stage III and IV) and in nocturnal growth hormone elevation. The recovery of a normal sleep EEG pattern and nocturnal growth hormone release in this patient suggests that the prolonged suppression of nocturnal growth hormone elevation and SWS reported in patients in remission following treatment of pituitary-dependent Cushing's disease may be related to factors other than steroid suppression.

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