SUN-696 - Hidden Visceral Adiposity in Non-Obese Hypercortisolism: The Hepatic Steatosis Index Identifies Visceral Fat Beyond Body Mass Index

Background and

Aim: Fat redistribution toward visceral depots is a hallmark of hypercortisolism and a driver of cardiometabolic risk. In patients without overt obesity, this phenotype may remain undetected by standard anthropometric indices. We examined whether the Hepatic Steatosis Index (HSI) identifies MRI-quantified visceral adiposity in non-obese patients across the hypercortisolism spectrum.

Methods: We conducted a cross-sectional study of participants with body mass index (BMI) < 30 kg/m² undergoing abdominal MRI for adipose tissue quantification, including patients with mild autonomous cortisol secretion (MACS, n=9), active Cushing's disease (CD, n=7), CD in remission (n=5), and healthy controls (HC, n=10), totaling 31 participants. Participants were stratified by BMI category: normal weight (BMI < 25 kg/m²), overweight (BMI 25–30 kg/m²), and the combined non-obese group (BMI < 30 kg/m²). Visceral adipose tissue (VAT) was measured on axial T2-weighted images at the L2–L3 intervertebral level using freehand regions of interest. Visceral adiposity was defined as VAT >130 cm². HSI performance for detecting MRI-defined visceral adiposity was evaluated using Fisher's exact test.

Results: Visceral adiposity was present in 18 of 31 participants (58.1%), with the highest prevalence in MACS (8/9, 88.9%), followed by CD in remission (3/5, 60%), active CD (4/7, 57.1%), and HC (3/10, 30%; p=0.08). In BMI-stratified analyses, within the overweight subgroup (BMI 25-30 kg/m², n=24), visceral adiposity remained highest in MACS (8/9, 88.9%), compared with CD in remission (3/4, 75%), HC (3/6, 50%), and active CD (2/5, 40%; p=0.215). In the normal-weight subgroup (BMI < 25 kg/m², n=7), visceral adiposity was observed in both patients with active CD (2/2, 100%), with no cases in CD in remission (0/1) or HC (0/4; p=0.03). HSI correctly classified all 13 participants without visceral adiposity as low-risk (specificity 100%) and detected 10 of 18 with pathological VAT (sensitivity 55.6%; p=0.001).

Conclusion: In non-obese patients across the hypercortisolism spectrum, visceral adiposity was nearly universal in MACS and present in the majority of the hypercortisolemic patients overall, independent of BMI stratum. HIS identifies visceral adiposity not captured by BMI and may serve as a practical screening tool in non-obese patients with hypercortisolism.

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