Background <p>The clinical relevance of post-dexamethasone cortisol levels below the conventional 1.8&#xa0;µg/dL threshold remains uncertain in patients with adrenal incidentalomas. We aimed to evaluate whether cortisol levels within the 1.0–1.8&#xa0;µg/dL range are associated with adverse cardiometabolic and inflammatory profiles.</p> Methods <p>In this retrospective, single-center cohort study, 199 patients with adrenal incidentalomas evaluated between 2023 and 2025 were included. Participants were stratified according to 1&#xa0;mg overnight dexamethasone suppression test (DST) results into two groups: &lt;1.0&#xa0;µg/dL (<i>n</i> = 112) and 1.0–1.8&#xa0;µg/dL (<i>n</i> = 87). Baseline hormonal (ACTH, DHEAS), metabolic (fasting glucose, HbA1c), and hematological parameters were obtained prior to DST to minimize the acute effects of dexamethasone. Systemic inflammation was assessed using the neutrophil-to-lymphocyte ratio (NLR) and systemic immune-inflammation index (SII). Group comparisons were performed using appropriate parametric or non-parametric tests. Multivariable logistic regression analysis was conducted to identify independent predictors of hypertension and diabetes mellitus.</p> Results <p>The prevalences of hypertension (71.3% vs. 42.9%, <i>p</i> &lt; 0.001) and diabetes mellitus (37.9% vs. 18.8%, <i>p</i> = 0.003) were significantly higher in the 1.0–1.8&#xa0;µg/dL group. These patients exhibited lower basal ACTH (<i>p</i> = 0.012) and DHEAS (<i>p</i> = 0.001) levels, along with higher fasting plasma glucose (<i>p</i> &lt; 0.001) and HbA1c (<i>p</i> = 0.003). Inflammatory markers, including NLR (<i>p</i> = 0.024) and SII (<i>p</i> = 0.040), were also significantly elevated. After adjustment for age, sex, tumor size, and LDL cholesterol, cortisol levels within the 1.0–1.8&#xa0;µg/dL range remained independently associated with both hypertension (OR = 2.74, 95% CI: 1.35–5.54, <i>p</i> = 0.005) and diabetes mellitus (OR = 2.39, 95% CI: 1.15–4.97, <i>p</i> = 0.020).</p> Conclusion <p>Cortisol levels between 1.0 and 1.8&#xa0;µg/dL were associated with increased systemic inflammation and an unfavorable cardiometabolic profile in patients with adrenal incidentalomas. These findings support the concept that cardiometabolic risk may exist along a continuum of post-DST cortisol values, even below the conventional 1.8&#xa0;µg/dL threshold. Patients within this intermediate cortisol range may benefit from closer clinical follow-up and cardiometabolic risk assessment, although prospective studies are needed to clarify its long-term clinical significance.</p> Clinical trial number <p>Not applicable.</p>