The effects of intraperitoneal calcitriol on calcium and parathyroid hormone

Abstract

Parathyroid suppression by intraperitoneal calcitriol (1,25(OH)2D3) during peritoneal dialysis. The purpose of this study was to determine if parathyroid hormone (PTH) suppression could be achieved by increasing calcium mass transfer (Ca MT) with high dialysate Ca (4 mEq/liter) or via intraperitoneal (i.p.) 1,25(OH)2D3 in patients undergoing continuous ambulatory peritoneal dialysis. Eleven patients were dialyzed for two months with standard Ca dialysate (3.5 mEq/liter) followed by two months with 4.0 mEq/liter Ca, then by three months of i.p. 1,25(OH)2D3. During the latter period, patients were randomized to groups whose dialysate contained either 3.5 mEq/liter or 4.0 mEq/liter Ca. We found that 4.0 mEq/liter Ca dialysate more than doubled Ca MT (37 +/- 17 mg/day to 84 +/- 6 mg/day) leading to a modest fall (P less than 0.05) in PTH levels (84 +/- 5.5% of controls). Ionized calcium levels did not change. With i.p. 1,25(OH)2D3, however, ionized calcium rose significantly (P less than 0.001) leading to a decline in PTH levels to 53.9 +/- 7.9% of control values. Serum 1,25(OH)2D3 levels rose from undetectable to 47.7 +/- 7.2 pg/dl (normal range 20 to 35). These studies indicate that increasing Ca MT using a 4.0 mEq/liter Ca dialysate leads to a small reduction in PTH concentrations. On the other hand, i.p. 1,25(OH)2D3 is well absorbed into the systemic circulation, raises ionized calcium levels, and leads to a marked suppression of PTH. Thus, i.p. 1,25(OH)2D3 may be a simple and effective means to suppress secondary hyperparathyroidism in patients undergoing CAPD.

Parathyroid hormone suppression by intravenous 1,25-dihydroxyvitamin D. A role for increased sensitivity to calcium.

“…Plasma levels of 1,25(OH)2D were measured by the method of Reinhardt et al (18). The characterization ofthe assay by our laboratory has been published elsewhere (19). All samples from each patient were determined in sextuplicate in the same assay.…”

Control of Mineral Metabolism in CAPD Patients

“…Calderaro et al [22] noted a negative balance of 50 ± 9 mg/day using a dialysate calcium of 3 mEq/1. We [23] found that patients not taking calcium supplements with ionized calcium levels of 4.72 ± 0.09 mg/dl had a net uptake of 37 ± 17 mg/day with the standard 3.5 mEq/1 calcium dialy sate. The net uptake more than doubled to 84 ± 6 mg/day with the use of a dialysate solution containing 4.0 mEq/1 of calcium.…”

“…This finding suggested that intravenous l,25(OH)2-vitamin D may directly suppress PTH secretion. Recent studies employing calcium infusions suggest that the mechanism may, in part, be due to increased sensitivity of the gland to ambient calcium levels [45], We, therefore, sought to determine if PTH suppression could be achieved by either increasing calcium mass transfer with a high dialysate calcium (4 mEq/1) or intraperitoneal 1,25(OH)2-vitamin D in patients undergoing CAPD [23], Eleven patients were dialyzed for 2 months with standard calcium dialysate (3.5 mEq/1), followed by 2 months with 4.0 mEq/1 cal cium dialysate and then 3 months with noc turnal dwells containing intraperitoneal l,25(OH)2-vitamin D. Ionized calcium and total calcium did not change with the higher dialysate calcium. However, both rose signif icantly with the use of intraperitoneal 1,25(OH)2-vitamin D. Phosphorus levels did not change.…”

Modifications of Endocrine-Metabolic Abnormalities of Uremia by Continuous Ambulatory Peritoneal Dialysis

“…For example, desferrioxamine increased dialysate aluminum 4-fold in an intoxicated patient, reducing plasma levels of aluminum [59]. As another example of drug therapy during CAPD, intra peritoneal absorption of 1,25-dihydroxyvitamin D3 can raise serum calcium and can depress serum PTH more effectively than increasing dialysis fluid calcium does [60].…”