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The negative Ca(2+) balance is involved in the stimulation of PTH secretion
Keitaro Yokoyama1, Shino Kagami, Ichiro Ohkido
1Division of Nephrology and Hypertension, Jikei University School of Medicine, Tokyo, Japan. keitaro@mrj.biglobe.ne.jp
Insights
Low calcium dialysate in hemodialysis can lead to a negative calcium balance, increasing parathyroid hormone (PTH) secretion. This may worsen secondary hyperparathyroidism in patients undergoing chronic kidney disease treatment.
Area of Science:
- Nephrology
- Endocrinology
- Mineral Metabolism
Background:
- Low calcium (Ca2+) dialysate is used in hemodialysis to prevent hypercalcemia.
- Its impact on calcium balance and parathyroid hormone (PTH) secretion requires further evaluation.
Purpose of the Study:
- To investigate the effects of low Ca2+ dialysate on calcium balance and PTH secretion in chronic hemodialysis patients.
Main Methods:
- Eighty-one chronic hemodialysis patients were switched from 3.0 mEq/l to 2.5 mEq/l Ca2+ dialysate.
- Calcium balance and serum intact PTH levels were monitored during and after the transition.
Main Results:
- A single hemodialysis session with low Ca2+ dialysate induced a negative calcium balance and increased serum intact PTH levels.
- After one month, serum intact PTH levels remained significantly elevated despite no changes in serum ionized calcium, phosphate, or magnesium.
Conclusions:
- Negative calcium balance during low Ca2+ hemodialysis stimulates PTH secretion, potentially offsetting serum calcium decrease.
- This suggests that low Ca2+ dialysate may exacerbate secondary hyperparathyroidism progression.
Abstract:
The low calcium (Ca(2+)) dialysate have been developed to diminish the risk of hypercalcemia with the administration of active vitamin D and Ca(2+) carbonate as phosphate binder. Today, increasing numbers of hemodialysis (HD) patients have been on the low Ca(2+) dialysate (Ca(2+) = 2.5 mEq/l). However, the clinical consequences of a negative calcium net-balance which may be induced by the use of low Ca dialysate are not well evaluated. In the present study, we explored the effects of low Ca(2+) dialysate on the calcium balance and the PTH secretion. Eighty one chronic HD patients (male/female: 47/34; mean age: 60.2 +/- 1.5 years; mean HD periods: 11.1 +/- 0.8 years) who had been dialyzed with 3.0 mEq/l Ca(2+) dialysate were studied. All patients were transferred to the low Ca dialysate, which actually brought about a negative net-balance in Ca (mean: -94.5 mg) and an increase in serum intact PTH levels (mean: +23.7%: p = 0.03) during a single HD session. However, no changes in serum ionized Ca(2+) were found in spite of negative Ca(2+) balance. One month after change to the low Ca(2+) dialysate (total 12 sessions in each case), serum intact PTH levels increased significantly (186.7 +/- 19.5 vs. 216.2 +/- 21.9 pg/ml: p = 0.01) in spite of the fact that no changes were found in serum ionized Ca(2+), Pi and Mg. This result indicates that the negative Ca(2+) balance during low-Ca(2+) hemodialysis-stimulated PTH secretion, which offset the decrease of serum Ca(2+); a trade-off phenomenon between negative Ca balance and PTH. This suggests that low Ca(2+) dialysate may exaggerate the progression of secondary hyperparathyroidism.