Endocrine Abstracts

Introduction: The aim of this study was to examine the relationship between serum calcium levels and renal function before and after curative parathyroidectomy (PTX) in patients with primary hyperparathyroidism (PHPT).

Objective and methods: A retrospective evaluation of 48 patient cases, corresponding ICD-10 code E21.0, was carried out, including demographic data and such biochemical markers as serum calcium, creatinine and estimated glomerular filtration rate (eGFR) levels, calculated using MDRD equation.

Results: From 48 participants included in the study 83,3% were female, while 16,7% were male patients. The mean age was that of 61,5 (min 29, max 81, SD 11,8); 14,6% of the patients were below the age of 50. At the time of diagnosis, 52,1% of the patients presented with mild hypercalcemia, 37,5%- moderate, while 6,3%- severe hypercalcemia, but the least- 4,2%- were normocalcemic. The mean calcium levels were those of 2,93 mmol/l (min 2,43, max 3,85, SD 0,31). Altogether 23,1% of the patients had reduced renal function, corresponding to recommended criteria for surgery, already at the time of diagnosis- 10,3% had eGFR that of stage 3a, 12,8%- stage 3b. Further data analysis, using Pearson correlation, revealed association between serum calcium levels and both creatinine and eGFR levels in firstly diagnosed patients – a moderate positive correlation between serum calcium and creatinine levels (r(37)=.597, P<0,01) and moderate negative correlation between calcium levels and eGFR (r(37)= -.559, P<0,01). Looking at dynamic changes, there was also found a moderate positive correlation between calcium levels in newly diagnosed patients and postoperative creatinine levels, measured at least 6 months up to one year after curative surgery (r(28)=.525, P<0,01). In addition, paired T test results showed statistically significant difference (t(25)= -3,6, P<0,01) when comparing creatinine levels as measured during the first (M=79,4, SD=28,4) and last (M= 87,2, SD= 32,4) patient assessment, i.e., before and at least six months after the surgery.

Conclusions: This study shows an association between serum calcium levels and such renal function biomarkers as creatinine and/or eGFR, both at the time of diagnosis and after curative surgery, suggesting higher serum calcium as a predictive factor for chronic kidney disease in patients with PHPT even after surgical intervention. While results of this study suggest that PTX didn’t halt the deterioration of renal function in PHPT patients, taking in account the small sample size, we would recommend further long-term large-scale controlled studies in order to evaluate surgical effects on renal function.