Hypercalcitoninemia in chronic kidney disease: an old issue, a new perspective?

Objective: Chronic kidney disease (CKD) has been reported in association with hypercalcitoninemia, but the calcitonin (Ct) values to expect in CKD patients are unknown. This study aimed to evaluate Ct levels in CKD patients using an accurate chemiluminescent immunoassay. Methods: Two population datasets were analyzed: Group 1 consisted of 9,450 anonymous subjects with Ct and creatinine measurements; this group was subdivided according to eGFR into a control series (eGFR ≥ 90 mL/min/1.73 m2, n = 4,294) and a CKD series (eGFR < 90 mL/min/1.73 m2, n = 4,022). Group 2 consisted of 135 patients with CKD (78.5% in stage 5). Renal function and Ct levels were retrospectively evaluated. Results: The Group 1 CKD series had a median Ct of 1.0 ng/L (IQR: 1.0-2.8 ng/L), 181 patients (4.5%) had Ct > 10 ng/L and ≤30 ng/L, and 35 patients (0.9%) had Ct ≥ 30 ng/L. Median Ct differed significantly according to CKD stage: 1.00 ng/L (IQR: 1.00-2.40 ng/L) in stage 2; 1.20 ng/L (IQR: 1.00-4.30 ng/L) in stage 3; 2.80 ng/L (IQR: 1.00-6.75 ng/L) in stage 4; and 4.55 ng/L (IQR: 1.00-11.30 ng/L) in stage 5 (P < 0.001). Median Ct in the control series was 1.0 ng/L (IQR: 1.0-2.9 ng/L). Ct levels >10 ng/L were significantly associated with CKD stage and were observed in 16.7% of stage 4 patients and 31.1% of stage 5 patients vs 4.3% of controls (P < 0.001). In Group 1, Ct levels were significantly correlated with creatinine (P < 0.001). In Group 2, median Ct was 3.7 ng/L (IQR: 1.0-7.0 ng/L), 25 patients (18.5%) had Ct levels >10 ng/L, and Ct levels were not associated with renal function. Conclusions: Ct levels may be mildly elevated in advanced CKD; until stage 3, the increase is negligible.