Endocrine Abstracts

Introduction: Although long-term complications such as nephrocalcinosis and renal insufficiency are well-known in chronic hypoparathyroidism (HPT), standardized investigations of their prevalence and causes are still lacking.

Objective: To systematically investigate the prevalence of renal calcifications and dysfunction and their predictors in a well-characterized cohort of patients with HPT.

Methods: Cross-sectional assessment of comorbidities in 169 patients with chronic HPT (disease duration >6 months). Further examinations included renal ultrasound and laboratory analysis of serum- and urine samples. Logistic regression analysis with backward selection was performed to identify risk factors for the development of nephrocalcinosis.

Results: Out of 169 patients (55 ± 13 yr, 76% female, disease duration 17±15 y), 88% had postoperative HPT. Prevalence of eGFR <60 ml/min/1.73m² was 21%, hypercalciuria 29%. Significant correlation between 24-h urine calcium excretion and spot urine calcium (r = 0.61, P < 0.0001) was observed. Renal ultrasound performed in 151 patients revealed renal calcifications in 9%, nephrocalcinosis in 7% and calculi in 3%. Significant differences between patients with renal calcifications (defined as nephrocalcinosis and nephrolithiasis) and without were found for 24-h urine calcium excretion (8.4 ± 5.9 mmol/d vs 6.1 ± 3.9 mmol/d, P < 0.05), albumin-corrected serum calcium (2.1 ± 0.2 mmol/l vs 1.99 ± 0.2 mmol/l, P < 0.02), serum phosphate (1.2 ± 0.3 mmol/l vs 1.3 ± 0.2 mmol/l, P < 0.05) and serum magnesium (0.73 ± 0.08 mmol/l vs 0.78 ± 0.07 mmol/l, P < 0.02). In contrast, no significant difference was found for prevalence of renal dysfunction and eGFR < 60 ml/min/1.73 m², serum calcium-phosporus product, serum 25-hydroxyvitamin D, 24 h urine calcium-to-creatinine ratio, daily calcium intake or duration of disease (24 ± 20 y vs 16 ± 14 y). In logistic regression analysis only serum calcium could be identified as potential risk factor, in contrast to 24-h urine calcium, serum phosphate, disease duration, as well as dosage of calcium and active vitamin D.

Conclusion: Here we report a high prevalence of eGFR <60 ml/min/1,73 m² and hypercalciuria but a low prevalence of renal calcifications. This reduction of eGFR is independent of type of HPT, daily calcium intake and disease duration. In our study, only fasting serum calcium represented a risk factor for the development of nephrocalcinosis. Further studies are warranted to elucidate the pathomechanism behind nephrocalcinosis in patients with HPT.