Different patterns of steroid secretion in patients with adrenal incidentaloma

We previously found that a remarkable number of patients with adrenal incidentaloma display partially autonomous cortisol secretion. The amount of hypercortisolism is insufficient to give clinical expression, but enough to inhibit, in some cases, normal adrenal tissue. Other researchers found with high frequency a partial deficiency of 21-hydroxylase. The aim of the present study was to make a combined evaluation of these aspects of adrenal steroidogenesis. Twenty patients (6 men and 14 women, aged 25-74 yr; median, 59 yr) with incidentally discovered adrenal masses were studied. All had an adrenal adenoma histologically proven or diagnosed on the basis of size (< or = 4.0 cm in all but 1) and computed tomography picture (hypodense homogeneous mass with well defined margins). The following parameters were used to evaluate the ACTH-cortisol axis: overnight 1-mg dexamethasone suppression (4 nonsuppressors), ovine CRH stimulation (blunted ACTH-cortisol response in 2 cases), circadian serum cortisol rhythm (blunted night/day ratio in 4 and increased 24-h mean in 1), and 24-h urinary free cortisol excretion (always within the normal range). Three patients had 2 concomitant alterations, and 5 had a single abnormality. Partial deficiency of 21-hydroxylase was assumed in 6 patients who showed an exaggerated 17-hydroxyprogesterone response to ACTH, with a peak value of more than 10 ng/mL (> 30 nmol/L), according to New's nomogram. No abnormalities of the ACTH-cortisol axis were found in these patients, with the exception of low amplitude cortisol rhythm in 1 case. Therefore, 2 distinct patterns, dysregulated and partially autonomous cortisol secretion, on the one hand, and reduced 21-hydroxylase activity, on the other, can be found in a high number of patients bearing an adrenal incidentaloma. They appear mutually exclusive, and the differentiation by endocrine testing is quite clear. Serum dehydroepiandrosterone sulfate was below the third percentile in 13 of 20 patients and could represent a specific marker of cortical adenomas. This finding was evenly distributed among patients with subclinical hypercortisolism or partial enzymatic defect; therefore, low serum dehydroepiandrosterone sulfate is not readily attributable to suppressed ACTH secretion, which actually occurs in only some patients with subclinical hypercortisolism.