Endocrine Abstracts

Primary hyperparathyroidism (PHPT) negatively affects renal function. It is known that chronic kidney disease is a predictor of cardiometabolic diseases. Cystatin C (cystC), an alternative measure of renal function, has been associated with adverse cardiovascular events and cardiometabolic risk factors. This study was aimed to evaluate serum cystC, its relationships with PTH and cardiometabolic risk in patients with PHPT.

The following parameters were measured in 193 consecutive patients (46 males, 147 females, age 59.4±15 years, mean±S.D.) affected with PHPT: weight, height, arterial blood pressure, serum calcium, phosphate, PTH, 25-hydroxyvitamin D₃, glucose, insulin, triglycerides, HDL cholesterol, creatinine and cystC; BMI and the insulin-resistance index HOMA were calculated and the glomerular filtration rate was estimated with the Modification of Diet in Renal Disease Study formula (eGFR).

Mean eGFR was 88.7±26.6 ml/min×1.73 m² in PHPT patients, where only two patients showed an eGFR <30 ml/min×1.73 m². Median cystC value was 0.87 mg/l (range 0.45–3.13, 25th–75th percentile 0.73–1.04 mg/l) and it negatively correlated with eGFR (r=−0.69, P<0.001). Moreover, cystC showed a significant positive correlation with total and ionized calcium as well as PTH levels (P<0.05). In multiple regression analysis, cystC was a stronger determinant of PTH (P<0.001) than eGFR (P=0.06). Patients with cystC levels >75th percentile were older, they had higher BMI, insulin, HOMA, triglycerides, lower HDL and a greater prevalence of arterial blood hypertension, diabetes mellitus and dyslipidemia (P<0.05). After adjusting for age, cystC levels correlated with BMI, insulin, HOMA, triglycerides and HDL cholesterol levels (P<0.05).

In conclusion, in PHPT patients serum cystC demonstrated a good correlation with eGFR. Moreover, CystC seems a better predictor of PTH elevation than eGFR in PHPT patients. Elevated cystC levels identify a subgroup of PHPT patients with a cluster of cardiometabolic risk factors. CystC might be a reliable marker to evaluate renal function and cardiometabolic risk in PHPT patients.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.