Effect of a Low Calcium Dialysate on Parathyroid Hormone Secretion in Diabetic Patients on Maintenance Hemodialysis

Abstract

Diabetic patients on maintenance dialysis often are characterized by a relative parathyroid hormone (PTH) deficiency and a form of renal osteodystrophy with low bone turnover known as adynamic bone. The goal of the present study was to determine whether a reduction in the dialysate calcium concentration would increase the predialysis (basal) PTH and maximal PTH level. Thirty-three diabetic maintenance hemodialysis patients with basal PTH values less than 300 pg/ml were randomized to be dialyzed with either a regular (3.0 mEq/liter or 3.5 mEq/liter, group I) or low (2.25 mEq/liter or 2.5 mEq/liter, group II) calcium dialysate for 1 year. At baseline and after 6 months and 12 months of study, low (1 mEq/liter) and high (4 mEq/liter) calcium dialysis studies were performed to determine parathyroid function. At baseline, basal (I, 126 ؎ 20 vs. II, 108 ؎ 19 pg/ml) and maximal (I, 269 pg/ml ؎ 40 pg/ml vs. II, 342 pg/ml ؎ 65 pg/ml) PTH levels were not different. By 6 months, basal (I, 98 ؎ 18 vs. II, 200 ؎ 34 pg/ml, p ‫؍‬ 0.02) and maximal (I, 276 pg/ml ؎ 37 pg/ml vs. II, 529 pg/ml ؎ 115 pg/ml; p ‫؍‬ 0.05) PTH levels were greater in group II. Repeated measures analysis of variance (ANOVA) of the 20 patients who completed the entire 12-month study showed that only in group II patients were basal PTH (p ‫؍‬ 0.01), maximal PTH ( p ‫؍‬ 0.01), and the basal/maximal PTH ratio ( p ‫؍‬ 0.03) different; by post hoc test, each was greater ( p < 0.05) at 6 months and 12 months than at baseline. When study values at 0, 6, and 12 months in all patients were combined, an inverse correlation was present between basal calcium and both the basal/maximal PTH ratio (r ‫؍‬ ؊0.59; p < 0.001) and the basal PTH (r ‫؍‬ ؊0.60; p < 0.001). In conclusion, in diabetic hemodialysis patients with a relative PTH deficiency (1) the use of a low calcium dialysate increases basal and maximal PTH levels, (2) the increased secretory capacity (maximal PTH) during treatment with a low calcium dialysate suggests the possibility of enhanced parathyroid gland growth, and (3) the inverse correlation between basal calcium and both the basal/maximal PTH ratio and the basal PTH suggests that the steady-state PTH level is largely determined by the prevailing serum calcium concentration.

Effects of Lowering Dialysate Calcium Concentration on Mineral and Bone Disorders in Chronic Hemodialysis Patients: Conversion from 3.0 mEq/L to 2.75 mEq/L

“…Importantly, we also found that patients with a higher baseline serum Ca level showed a greater increase in serum PTH value and PTH ratio after 1 year. These results were not unexpected, because patients with a higher pre‐dialysis serum Ca level showed a greater decline in the post‐dialysis Ca level, stimulating PTH secretion more intensely . Thus, patients with a higher baseline serum Ca level should be carefully managed to avoid SHPT progression.…”

Association between Very Low PTH Levels and Poor Survival Rates in Haemodialysis Patients: Results from the French ARNOS Cohort

“…Apart from surgical parathyroidectomy (PTX) and calcimimetics, many factors have been associated with an increased risk for ABD: old age, low protein intake and phosphate level [8], high dialysate calcium [9], excessive use of calcium and aluminium-based phosphate binders [10], excessive use of calcitriol [11], peritoneal dialysis [12], skeletal resistance to iPTH [5], and diabetes [13]. …”

Calcium balance in hemodialysis: More uncertainty than certainty

“…On the other hand, low DCa is associated with hypocalcaemia which may lead to cardiac rhythm disturbances, typically QTc prolongation, myocardial ischemia, and stunning, and hypotension due to decreased vascular resistance and lower cardiac output. Adynamic bone disease : In the presence of adynamic bone disease the use of a low DCa, probably 2.5 mEq/L, may be appropriate as it has been shown to increase serum PTH and bone‐specific alkaline phosphatase . Concomitant restriction of noncalcium‐based phosphate binders and discontinuing or reducing the dose of active vitamin D sterols may also be warranted …”