ABSTRACT
Data are presented concerning a 60-year-old woman with untreated congenital adrenocortical hyperplasia due to 21-hydroxylase deficiency, who presented with a tumour of the left adrenal gland. Steroid excretion was partly suppressed with dexamethasone. After removal of the tumour, the excretion of several steroid fractions decreased substantially, but suppression by dexamethasone remained inadequate. Preoperatively, plasma ACTh was elevated in the afternoon and decreased only slightly after dexamethasone administration. After surgery, cortisol secretion decreased markedly, whereas ACTH dysregulation became more prominent. Negative feedback failure precluded the use of normal suppressive therapy with low doses of glucocorticosteroids and led to the therapeutic removal of the right adrenal gland, which showed histological signs of nodular hyperplasia.