Congenital adrenal hyperplasia is a very rare cause of adrenal incidentalomas in Sweden.

Background: Undiagnosed congenital adrenal hyperplasia (CAH) can cause adrenal incidentalomas, but the frequency is unclear.

Objectives: This study aimed to investigate the prevalence of CAH in a population with adrenal incidentalomas and report the clinical characterization.

Material And Methods: This was a prospective study performed at a regional hospital from 2016 to 2021. Patients with adrenal incidentalomas were investigated with an adrenocorticotropic hormone (ACTH)-stimulation test in addition to hormonal workup. Serum cortisol and 17-hydroxyprogesterone (17OHP) were analyzed. Individuals with a basal or stimulated 17OHP ≥30 nmol/L were classified as suspicious non-classic CAH, and a -gene analysis was performed in these subjects.

Results: In total, 320 individuals with adrenal incidentalomas were referred to the center, and of these individuals, an ACTH-stimulation test was performed in 222 (median age, 67 (24-87) years; 58.6% women; and 11.7% with bilateral lesions). None of the individuals presented a basal 17OHP ≥30 nmol/L, but there were 8 (3.6%) who did after ACTH stimulation. Four of these subjects (50%) presented bilateral lesions, and the tumor size was larger compared to that of the individuals with a stimulated 17OHP <30 nmol/L (median, 38 (19-66) vs. 19 (11-85) mm, p=0.001). A variation (p.Val282Leu) was detected in one of the eight subjects with a stimulated 17OHP ≥30 nmol/L, i.e., the patient was a heterozygotic carrier. None of the eight subjects presented with cortisol insufficiency or clinical signs of hyperandrogenism.

Conclusions: The prevalence of non-classic CAH in an adrenal incidentaloma cohort was 3.6% based on stimulated 17OHP and 0% based on gene analysis. CAH should be considered in AI management in selected cases and confirmed by genetic analysis.