Routine immune signatures track cortisol and complications in Cushing’s syndrome

Routine blood-count measures were associated with both biochemical cortisol excess and selected complications in a retrospective study of 202 patients with endogenous Cushing’s syndrome. The strongest and most consistent signals came from eosinophil depletion and an elevated neutrophil-to-lymphocyte ratio, or NLR: both tracked urinary, midnight and morning cortisol measurements. Individual markers also differed in their links with electrolyte abnormalities, diabetes and fracture. An exploratory composite combining NLR, eosinophil depletion and low prognostic nutritional index was associated with the number of clinical domains affected, but it did not outperform NLR alone and requires external validation.

The single-centre study, conducted at the First Hospital of Jilin University, included 71 patients with adrenocortical adenoma, 122 with Cushing’s disease and nine with ectopic adrenocorticotropic hormone syndrome. Participants were admitted between December 2012 and December 2022, and analysis used clinical and laboratory data recorded before definitive treatment. Researchers examined seven immune-related measures derived from routine blood counts: absolute neutrophil, lymphocyte and eosinophil counts; NLR; systemic immune-inflammation index; systemic inflammation response index; and prognostic nutritional index, or PNI. These were evaluated against three biochemical cortisol measures: 24-hour urinary free cortisol, midnight serum cortisol and 8 a.m. serum cortisol.

After adjustment for age, sex and the cause of Cushing’s syndrome, all seven immune markers remained significantly associated with each cortisol measure. NLR rose with cortisol, with correlations of 0.639 for 24-hour urinary free cortisol, 0.640 for midnight cortisol and 0.627 for morning cortisol. Eosinophil count showed the opposite pattern, with correlations of −0.715, −0.608 and −0.619, respectively. In multivariable models, each one-standard-deviation increase in log-transformed NLR was associated with a 0.647 increase in log-transformed urinary free cortisol, while a one-standard-deviation increase in log-transformed eosinophil count was associated with a 0.687 decrease. The corresponding NLR coefficient for midnight cortisol was 0.464. These results indicate statistical associations within this cohort, not evidence that the blood markers caused cortisol elevation.

Complication-specific models provided a more selective picture. They excluded the nine patients with ectopic ACTH syndrome because their unusually high cortisol levels and small subgroup size could disproportionately influence estimates, and they adjusted for age, sex, aetiology and 24-hour urinary free cortisol. After false-discovery-rate correction, significant associations remained for hypokalaemia, hypophosphataemia, diabetes and fracture. For hypophosphataemia, each one-standard-deviation increase in log-NLR was associated with 2.86 times the odds of the condition, with a 95% confidence interval of 1.39 to 6.33. Eosinophil depletion was associated with hypophosphataemia with an odds ratio of 2.58, while low PNI had an odds ratio of 2.29.

Associations differed across outcomes. For hypokalaemia, log-NLR, eosinophil depletion, log systemic immune-inflammation index and low PNI were each linked with higher odds, with adjusted odds ratios ranging from 1.70 to 2.27. For diabetes, only the systemic immune-inflammation index remained significant after correction, with an odds ratio of 1.94 and a 95% confidence interval of 1.23 to 3.07. Fracture was associated with log-NLR, log systemic immune-inflammation index and low PNI. The strongest of these was low PNI, associated with 2.52 times the odds of fracture, with a 95% confidence interval of 1.60 to 3.96. No immune-marker association with increased relative wall thickness survived correction in the primary analysis.

The researchers also constructed an exploratory cortisol-related immune score, or CRIS, by equally averaging three standardised components: log-NLR, eosinophil depletion expressed as the negative logarithm of eosinophil count plus a small offset, and negative PNI. Higher values represented a more pronounced peripheral immune profile associated with cortisol excess. In 182 patients with available data, the mean selected complication-domain burden rose from 1.50 in the lowest CRIS quartile to 2.47 in the highest. Involvement of at least two domains increased from 39.1% to 77.8%, while the proportions with upper-quartile morning cortisol rose from 2.3% to 69.8% and those with upper-quartile urinary free cortisol rose from 5.0% to 61.5%.

After adjustment for age, sex and aetiology, each one-standard-deviation increase in CRIS was associated with a 20% higher complication-domain burden score, expressed as an incidence rate ratio of 1.20 with a 95% confidence interval of 1.07 to 1.35. It was also associated with multidomain complication involvement, with an odds ratio of 1.90 and a 95% confidence interval of 1.32 to 2.82. The burden score counted affected domains rather than their severity: electrolyte involvement, hypertension, diabetes and fracture each contributed one point. The association with burden remained after additional adjustment for urinary free cortisol, with an incidence rate ratio of 1.29, but did not hold in the adrenocortical adenoma subgroup when examined separately.

CRIS did not demonstrate clear added value over NLR. Among patients with adrenocortical adenoma or Cushing’s disease, its area under the ROC curve for multidomain complication involvement was 0.737, compared with 0.738 for log-NLR; the difference was not significant. Adding CRIS to a model already containing log-NLR did not significantly improve fit, and tenfold cross-validated AUCs were similar, at 0.711 and 0.706. The components also share information because both NLR and PNI depend on lymphocyte count. Overall, CRIS is best viewed as an experimental summary of several correlated blood measures rather than a validated diagnostic tool or replacement for established endocrine, imaging and clinical assessments.

The study has important constraints. Its retrospective, single-centre design prevents causal or temporal conclusions and limits generalisability. The ectopic ACTH group was very small, and some complications had few events, reducing precision. Urinary free cortisol was available for 173 patients, echocardiographic data for 171, and other cortisol measurements were not systematically available for every participant. Fractures were identified from records and imaging reports without routine screening for asymptomatic vertebral fractures, while the timing of diabetes relative to Cushing’s syndrome was limited. Selected complications were assessed at the index admission and analysed as prevalent conditions. Although multiple imputation and sensitivity analyses produced broadly similar results, these constraints mean the findings should be treated as exploratory.

The central finding is that inexpensive, routinely measured blood indices carry a measurable statistical signal in endogenous Cushing’s syndrome. Eosinophil depletion and increased NLR consistently accompanied higher cortisol, while their associations with electrolyte disorders, diabetes and fracture were selective rather than universal. That variation matters: a marker may reflect aspects of cortisol excess without representing every clinical consequence. The exploratory CRIS summarized three immune features and tracked selected complication burden, but its performance did not surpass NLR alone. Prospective studies in larger, independent cohorts are needed to determine whether these measurements can add clinically useful information beyond established biochemical testing and careful assessment of complications.

Subject of Research: Associations between routine blood-derived immune markers, cortisol excess and selected complications in endogenous Cushing’s syndrome

Article Title: Routine blood-based immune signatures in endogenous Cushing’s syndrome: associations with cortisol excess and selected complication burden

Article References: Cai, Y., Tan, S., Liu, S., Wang, M., Liu, T., & Wang, G. (2026). Routine blood-based immune signatures in endogenous Cushing’s syndrome: associations with cortisol excess and selected complication burden. Frontiers in Endocrinology, 17, Article 1961986. https://doi.org/10.3389/fendo.2026.1961986

Image Credits: AI Generated

DOI: 10.3389/fendo.2026.1961986

Keywords: Cushing’s syndrome, hypercortisolism, eosinophil depletion, neutrophil-to-lymphocyte ratio, blood biomarkers, complication burden, cortisol, retrospective study, Routine, blood-based, immune, signatures