title: Relationship between the serum parathyroid hormone and magnesium levels in continuous ambulatory peritoneal dialysis (CAPD) patients using low-magnesium peritoneal dialysate.
abstract: BACKGROUND
  Patients on continuous ambulatory peritoneal dialysis (CAPD) have increased risk of low-turnover bone disease and relative hypoparathyroidism. Recently, it has been believed that magnesium plays an important role in regulating secretion of parathyroid hormone (PTH). The aim of this study was to evaluate the relationship between serum PTH and serum magnesium as a factor increasing the frequency of relative hypoparathyroidism.
  
  
  METHODS
  We analyzed the data of 56 patients who had been on CAPD for more than 6 months without any significant problems. No patient had been previously treated with vitamin D or aluminum hydroxide. The patients had used peritoneal dialysate with the magnesium concentration of 0.5 mEq/L. Biochemical parameters, such as BUN, creatinine, alkaline phosphatase bony isoenzyme, total protein, albumin, total calcium, ionized calcium and intact parathyroid hormone level were measured.
  
  
  RESULTS
  The mean serum magnesium level was 1.99 +/- 0.36 mEq/L. Among total 56 patients, 15 patients (26.8%) showed hypermagnesemia (serum magnesium > 2.2 mEq/L) and 5 patients (8.9%) showed hypomagnesemia (serum magnesium < 1.6 mEq/L). Among all 56 patients, serum iPTH (intact PTH) level was not correlated with serum magnesium level. However, it was inversely correlated with serum total calcium and ionized calcium levels, respectively (r = -0.365, p = 0.006; r = -0.515 p < 0.001). Among 49 patients whose serum iPTH level was less than 300 pg/mL, serum iPTH level was inversely correlated with serum magnesium level (r = -0.295, p = 0.039) and inversely correlated with serum total calcium and ionized calcium levels, respectively (r = -0.546, p < 0.001; r = -0.572 p < 0.001). Among 49 patients whose serum iPTH level was less than 300 pg/mL, lower iPTH group (serum iPTH < 120 pg/mL) showed higher serum magnesium level (p = 0.037), higher serum total calcium level (p < 0.001) and lower bone isoenzyme of alkaline phosphatase level (p < 0.001) than those of higher iPTH group (120 pg/mL < or = serum iPTH < 300 pg/mL).
  
  
  CONCLUSIONS
  Among the CAPD patients whose serum iPTH level was less than 300 pg/mL, there was a significant inverse correlation between serum iPTH level and serum magnesium level. This study indicates that not only serum calcium level but also serum magnesium level are important in the regulation of serum iPTH levels of CAPD patients who have been dialyzed by low-magnesium peritoneal dialysate.
authors.affiliation: Department of Internal Medicine, Chonnam National University Medical School, Kwangju, Korea.
authors.forename: Min Seok
authors.initials: MS
authors.lastname: Cho
authors.forename: Kyun Sang
authors.initials: KS
authors.lastname: Lee
authors.forename: Youn Kyoung
authors.initials: YK
authors.lastname: Lee
authors.forename: Seong Kwon
authors.initials: SK
authors.lastname: Ma
authors.forename: Jeong Hee
authors.initials: JH
authors.lastname: Ko
authors.forename: Soo Wan
authors.initials: SW
authors.lastname: Kim
authors.forename: Nam Ho
authors.initials: NH
authors.lastname: Kim
authors.forename: Ki Chul
authors.initials: KC
authors.lastname: Choi
mesh_terms: D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D002118:Calcium / Q000097:blood; D012080:Chronic Kidney Disease-Mineral and Bone Disorder / Q000209:etiology; D015314:Dialysis Solutions; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000150:complications / Q000628:therapy; D008274:Magnesium / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D010531:Peritoneal Dialysis, Continuous Ambulatory / Q000009:adverse effects* / Q000379:methods; D010710:Phosphates / Q000097:blood
chemical_list: D015314:Dialysis Solutions; D010281:Parathyroid Hormone; D010710:Phosphates; D000469:Alkaline Phosphatase; D008274:Magnesium; D002118:Calcium