Leukocytosis in Cushing's syndrome persists post-surgical remission and could predict a lower remission prognosis in patients with Cushing's disease.

Context: Leukocytosis frequently noted in Cushing's syndrome (CS), along with other blood cell changes caused by direct and indirect cortisol effects.

Objective: Assess baseline white blood cell (WBC) profile in CS patients compared to controls and WBC changes pre- and post-remission after surgical treatment for CS.

Design: A comparative nationwide retrospective cohort study.

Setting: Data from Clalit Health Services database.

Patients: 297 patients (mean age 51 ± 16.1 years, 73.0% women) with CS and 997 age-, sex-, body mass index-, and socioeconomic status-individually matched controls. Ectopic CS or adrenal cancer patients were excluded.

Main outcome measure: Mean WBC, neutrophils, and neutrophil-to-lymphocyte ratio (NLR) two-years before and after pituitary or adrenal surgery. WBC and neutrophils are expressed as Kcells/µl.

Results: At baseline, leukocytosis was observed in 21.5% of patients with CS vs. 8.9% of controls (P < 0.001). Patients with CS had significantly higher WBC (8.8 ± 2.88 vs. 7.54 ± 2.45, p < 0.0001), neutrophils (5.82 ± 2.38 vs. 4.48 ± 1.97, p < 0.0001), and NLR (3.37 ± 2.63 vs. 2.27 ± 1.86, p < 0.0001) compared to controls, regardless of pituitary or adrenal source of hypercortisolemia. Post-surgery, patients with CS experienced significant decreases in mean WBC (-0.57 ± 2.56, p < 0.0001), neutrophils (-0.84 ± 2.55, p < 0.0001), and NLR (-0.63 ± 2.7, p < 0.0001). Despite achieving disease remission, patients with CS still had higher WBC (8.11 ± 2.4 vs. 7.46 ± 2.17, p = 0.0004) and neutrophils (4.71 ± 2.10 vs. 4.41 ± 1.87, p = 0.03) compared to controls. Patients with CD and baseline leukocytosis had lower remission rate than those with normal WBC (36.7% vs. 63.9%, p = 0.01).

Conclusions: At diagnosis, CS patients have elevated WBC, neutrophils, and NLR compared to controls. Remission does not normalize WBC levels in all patients, and baseline leukocytosis predicts a poorer remission prognosis in CD.