Subclinical hypercortisolism: debatable or visible on the lightbox?

Abstract

Adrenal nodules unrelated to clinically overt adrenal disease became visible more than 120 years ago ever since the first autopsy studies [1]. Nowadays, through the development of modern radiology modalities, adrenal nodules previously identified only at autopsy or surgery, are easily visible during imaging of the abdomen. The importance of this for the practicing endocrinologist is highlighted by the fact that hardly a week goes by without a patient being referred for further evaluation of an incidentally depicted adrenal mass. Despite, however, the high prevalence of adrenal incidentalomas, about 4 % in the middle-age population, approaching 7 % in the elderly ones [2, 3], and an ongoing stream of published papers, its relevance for the patient remains in many occasions largely inconclusive. The vast majority of adrenal incidentalomas are benign adrenocortical adenomas although rare entities, such as myelolipomas, cysts, ganglioneuromas, onconcytomas, may also be encountered. A significant proportion of patients, about 15 %, have bilateral lesions [4]. Since most adrenal incidentalomas arise from adrenal tissue, a substantial proportion of them are functional in terms of autonomous production of various adrenal hormones, including cortisol, aldosterone, catecholamines or rarely androgens. Subclinical hypercortisolism (SH), defined by an abnormal endocrine work-up indicating autonomous cortisol secretion in the absence of obvious clinical stigmata of Cushing’s syndrome, is by far the most commonly encountered abnormality. It is detected in a varying proportion of subjects, between 1 and 47 %, depending on the diverse criteria used to define it [5]. The finding of an adrenal mass undoubtedly raises concerns about the possibility of malignancy but adrenocortical cancer in this context is rare, especially when the size of the lesion is less than 4.0 cm, as is the case with most adrenal incidentalomas [6]. Thankfully, differentiation between benign and malignant adrenal lesions is visible with much accuracy with current imaging techniques. On CT scanning, which is the modality of choice for evaluating the adrenal glands, adrenocortical adenomas are well-circumscribed ovoid masses with typically low attenuation values (less than 10 HU) on unenhanced images, due to the high content in lipids. The 20–30% of lipid-poor adrenal adenomas that exhibit higher attenuation values can be further evaluated either using contrast washout techniques or MRI scans. Benign adenomas on CT show an absolute and a relative percentage of contrast washout of more than 60 and 40 %, respectively. MRI may provide additional information for the few remaining indeterminate lesions, using T1-weighted, T2-weighted, and especially chemical shift imaging (CSI); benign adenomas are homogenous, have low or equal signal intensity compared to the liver on T2-weighted images and demonstrate significant signal intensity loss on out-of-phase CSI compared to the in-phase images. Thus, radiology has a major role in identifying the rare cases of malignancy among adrenal incidentalomas through the initial imaging phenotype combined with a repeat scan to evaluate potential rapid and significant increase in size. In this Endocrine issue Olsen et al. [7] in a multicentre, prospective study attempt to expand the usefulness of imaging visibility toward a functional perspective. The authors investigated 235 patients presenting with benign appearing incidentally detected adrenal masses and correlated CT findings such as unenhanced attenuation value, size, and bilaterality with the hormonal work-up for the presence of SH. Previous observational data have shown a consistent relationship between the size of the adenoma D. A. Vassiliadi S. Tsagarakis (&) Department of Endocrinology, Diabetes and Metabolism, Evangelismos Hospital, 45 Ipsilantou St, 106 76 Athens, Greece e-mail: stsagara@otenet.gr