Asymptomatic Adrenal Tumors Also May Increase Risk of Type 2 Diabetes, Study Suggests

Undiagnosed tumors on the adrenal glands — called adrenal incidentalomas, because they are found by chance — may be more prevalent than previously thought and also may be linked to an increased risk of type 2 diabetes, a new study has found.

The study, “Adrenal incidentalomas are tied to increased risk of diabetes: findings from a prospective study,” was published in The Journal of Clinical Endocrinology & Metabolism.

Sometimes, diagnostic imaging scans reveal findings unrelated to what prompted the imaging in the first place, such as a previously unidentified tumor. These tumors are appropriately called incidentalomas and their  detection is becoming more common as imaging technology becomes more sophisticated.

This study focused on adrenal incidentalomas, which are masses found serendipitously on the adrenal gland.

Adrenal tumors cause about 15% of Cushing’s syndrome cases. Some of these tumors also induce mild elevations in cortisol secretion that do not prompt obvious signs of Cushing’s, but may have health consequences because cortisol increases the risk of metabolic and cardiovascular diseases.

Seeking to determine the frequency of adrenal incidentalomas and whether patients with such tumors have an increased incidence of other conditions, researchers in Italy examined clinical data from all patients who underwent a computed tomography (CT) scan at their center from January 2017 to June 2018.

The scans were reviewed by an experienced radiologist who specifically looked for adrenal tumors. The study excluded all patients with confirmed or suspected cancer; it consisted mainly of people who were getting CT scans done for abdominal pain, other abdominal symptoms, or as part of a urological examination.

In total, 601 people (average age 63.5 years) had their scans analyzed, and 44 (7.3%) had adrenal incidentalomas.

This is a relatively higher rate than usually reported Researchers proposed this could be due to improved methodology (i.e., expert reassessment of the images, which has not always been done).

They noted that this figure is “close to that of autopsy series,” suggesting that adrenal incidentalomas may be more frequent than previously appreciated, although there is the caveat that the majority of people included in the study were referred to CT scans because they were experiencing some kind of symptoms.

Compared to patients without adrenal incidentalomas, those with such tumors were more frequently male (72.7% vs. 53.7%) and had significantly higher average body mass index, a measure of body fat (27.6 kg/m² vs. 25.6 kg/m²), and waist circumference (101.2 cm vs. 92.7 cm).

Rates of type 2 diabetes also were higher among people with adrenal incidentalomas (31.8% vs. 14.2%). Subsequent statistical analyses that accounted for other relevant factors found a significant association between diabetes and adrenal incidentalomas.

An analysis of the people with adrenal incidentalomas based on their cortisol levels revealed no significant differences in terms of demographic and clinical characteristics among those with lower or higher levels, although the relatively small sample size makes it difficult to draw firm conclusions in this regard.

“[T]he findings support the association between adrenal incidentalomas and type 2 diabetes,” the researchers stated.

This association has been identified before, but previous studies have typically looked at the incidence of adrenal tumors only in people who have diabetes.

“[O]ur findings are free from ascertainment bias, since patients with adrenal incidentalomas were drawn from a cohort of outpatients showing a risk of diabetes comparable with the background population of our region,” the researchers wrote. “The prospective recruitment of our series, and the fact that it was not enriched a priori by diabetic patients, provide strong support to the concept.”