Hormonal activity of adrenal incidentalomas: results from a long-term follow-up study

To investigate the natural course of apparently benign adrenal incidentalomas with no overt hyperfunction at diagnosis, as their clinical significance and appropriate management are still controversial.

Prospective long-term follow-up study of patients with adrenal incidentalomas with periodic hormonal and morphological evaluation.

A total of 77 patients with incidental adrenal masses, diameter 1.0-6.0 cm (median 2.5 cm), were submitted to a hormonal assessment of adrenal function at diagnosis. This was repeated, together with an adrenal CT scan, 12 months later and then every 12-24 months, for a period of 12-154 months (mean 62.7 +/- 31.9, median 60.0).

At diagnosis, 57 patients had normal adrenal function and 20 had subclinical Cushing's syndrome. During follow-up, adrenal function remained normal in 49 patients, subclinical Cushing's syndrome was confirmed in 12, whilst intermittent subclinical autonomous cortisol hypersecretion was found in 12 patients. Overt endocrine disease was diagnosed in 4 patients (Cushing's syndrome in 2 and phaeochromocytoma in 2). A change in mass size (> or = 0.5 cm) was observed in 26 patients (enlargement in 20--including patients who developed overt hyperfunction--with no signs of malignancy and reduction in size in 6).

Subclinical autonomous cortisol hypersecretion is the most frequent hormonal abnormality in patients with adrenal incidentalomas, and may be intermittent in a significant percentage of cases. Few patients develop overt endocrine disease. A growth tendency is observed in some adrenal incidentalomas without evidence of malignant transformation and occasionally can be related to development of overt hyperfunction. These findings indicate the need for periodic hormonal and morphological evaluation for several years.