Patients with primary hyperparathyroidism (PHPT) are at risk of chronic kidney disease (CKD). PHPT patients (n=190, 146 females and 44 males, aged 59.7±14.2 years) and non-hypertensive, non-diabetic age- and sex-matched healthy controls were evaluated for serum cystatin C and creatinine. PHPT patients and controls with established CKD were excluded. Serum cystatin C was measured by immunonephelometric assay and calculation of estimated glomerular filtration rate (eGFR) was based on serum creatinine and cystatin C (eGFRcr-cys) using the CKDEPI equation. Serum cystatin C well correlated with serum creatinine in PHPT patients (r=0.594, P=0.0001), while mean cystatin C level was significantly higher in PHPT patients than in healthy controls (0.93±0.02 mg/l vs 0.78±0.01 mg/l, P=0.001). In particular, among PHPT patients with eGFRcr >60 ml/min per 1.73 m2, 18.4% had cystatin C levels >1.03 mg/l (95th percentile of controls values), consistent with a preclinical kidney disease. These patients had higher HOMA-IR values and were more hypertensive. In PHPT patients, cystatin C levels positively correlated with total and ionized calcium (r=0.151, P=0.024 and r=0.259, P=0.004) and with PTH (r=0.176, P=0.01). Using the eGFRcr-cys equation, CKD (stages G3a, 3b, and 4) was diagnosed in 13.7% of PHPT patients. CKDPHPT patients had higher total and ionized calcium, were older, more frequently males, heavier, more insulin-resistant and more frequently affected with hypertension. Any significant correlation with the occurrence of kidney stones could be detected. Regression analysis identified hypertension and HOMA-IR values as the independent variables able to predict eGFRcr-cys in PHPT patients. Considering the occurrence of cardiovascular diseases (CVD) (coronaropathy, arithmopathy, and cerebral vasculopathy), after adjustment for age and sex, CVD was positively correlated with cystatin C levels (β 0.305±0.109; P=0.006) and negatively with eGFRcr-cys values (β −0.005±0.002; P=0.011). In conclusion, elevated cystatin C levels were cross-sectionally associated with key CVD risk factors and with CVD diseases in PHPT patients as in the general population.
Disclosure: This work was supported by IRCCS Policlinico San Donato Research Found.