MO095: Normocalcaemic Hyperparathyroidia Diagnosed by Calcium Load. (3rd May 2022)

• Record Type: Journal Article
• Authors: Lemoine, Sandrine; Dang, Julien; Dubourg, Laurence
• Is Part Of: Nephrology dialysis transplantation. Volume 37(2022)Supplement 3
• Publication Date: 2022-05-03
• Subjects: Nephrology -- Periodicals; Hemodialysis -- Periodicals; Kidneys -- Transplantation -- Periodicals; Hemodialysis; Kidneys -- Transplantation; Nephrology; Periodicals; 616.61
• DOI: 10.1093/ndt/gfac065.001
• Languages: English
• ISSNs: 0931-0509

Abstract

Abstract: BACKGROUND AND AIMS: Calcium load is usually used in clinical practice to diagnose a normocalcaemic hyperparathyroidia in stone disease. However, the calcium load developed by Pak and colleagues has been described in very few patients. We aimed to provide data about calcium load in a bigger cohort of patients. METHOD: We included retrospectively 115 patients who underwent a calcium load for stone disease or hypercalciuria with a basal increased PTH. At basal state, ionized calcium (iCa 2+ ), PTH, phosphate urinary Calcium to creatinine ratio (UCa/creat), 25 OHvit D and 1–25 OHvit D were measured. Patients ingested 1g of calcium and iCa 2+ PTH, phosphate and UCa/creat were measured after 2 h and 4. Calcium load was interpreted based on Pak's publications. Normocalcaemic hyperparathyroidia was defined by fasting urinary calcium/creatinine ratio >0.35 mmol/mmol associated with a non-adapted PTH to ionized calcium (iCa 2+ ) after calcium load and absorptive hypercalciuria. Renal hypercalciuria is defined by fasting and absorptive hypercalciuria with an adapted decrease of PTH to iCa 2+ . RESULTS: At a basal state, PTH was 88 (±19) ng/L, calcium was 2.36 (±0.14) mmol/L, iCa 1.23 (±0.08) mmol/L, calcium excretion fraction was 1.5 (0.85)% and phosphataemia was 0.88 (±0.14) mmol/L. The mean fasting Ca/creat ratio was 0.4 mmol/mmol. A total of 21% were hypercalcemic (iCa > 1.30 mmol/L). iCa 2+ was 1.28 (±0.07) 2 h after calcium load (H2) and was 1.27 (±0.07) mmol/L 4 h after calcium load (H4). The mean decrease in PTH was 32% after H2 and 44% after H4. Urinary Ca/creat was 0.55 and 0.73 mmol/mmol after H2 and H4, respectively. A total of 27% of patients had a UCa/creat increase of >0.5 mmol/mmol after H2, and 47% after H4. A total of 72% had a calcium excretion fraction of >1%. Normocalcaemic hyperparathyroidia was diagnosed in 64% of these patients. In Normocalcaemic hyperparathyroidia, mean PTH was 91 (±21) ng/L, the mean decrease of PTH was 35% and 27% after H2 and H4, respectively. The mean iCa 2+ increased from 1.24 (±0.07) to 1.28 (±0.07) mmol/L. UCa/creat increased from 0.45 (±1.26) to 0.71 (±1.26) and 0.81 (±1.26) after H2 and H4, respectively. The 1–25 OH vit D was 159 (±55) pmol/L. In renal hypercalciuria, mean PTH was 66 (±26) ng/L, 42 (±20) after H2 and 30 (±13) after H4. The mean decrease in PTH was 65% after H4. Mean iCa 2+ increased from 1.24 (±0.07) to 1.27 (±0.07) mmol/L. UCa/creat increased from 0.33 (±0.19) to 0.37 (±0.25) and 0.68 (±0.44) mmol/mmol after H2 and H4, respectively. The 1–25 OH vit D was 130 (±67) pmol/L. Basal PTH is significantly higher in normocalcaemic hyperparathyroidia compared with renal hypercalciuria, but there is no difference in fasting UCa/creatinine ratio between both group. The 1–25 OHvit D level was significantly increased in normocalcaemic hyperparathyroidia. CONCLUSION: Calcium load allows to discriminate patients with basal increased PTH between normocalcaemic hyperparathyroidia and renal hypercalciuria. We provide new data to help physicians in clinical practice.