Serum Magnesium Concentration and PTH Levels. Is Long-Term Chronic Hypermagnesemia a Risk Factor for Adynamic Bone Disease?

Abstract

The observation that some subjects with low PTH had elevated plasma magnesium (Mg) levels prompted us to analyze in 41 patients on maintenance hemodialysis for 44 +/- 36 months, their serum Mg concentrations, and the relationship between plasma Mg and PTH levels. The mean serum Mg concentration was 2.4 +/- 0.2 mg/dl. Twenty-four out of the 41 subjects (58.5%) had hypermagnesemia (serum Mg above 2.5 mg/dl). Patients were classified into 3 groups according to their PTH level: Group A, low PTH (below 120 pg/ml); group B, adequate PTH (120-250 pg/ml); and group C, high PTH (above 250 pg/ml). There were no differences among groups according to number of subjects, age, sex, time on dialysis, renal disease, serum calcium, phosphorus, bicarbonate, vitamin D or aluminum concentrations. Doses of calcium carbonate and aluminium hydroxide were also similar in all groups. Curiously, although the differences were not statistically significant, the total cumulative intake of calcium and aluminium were less in group A than in the other groups. Interestingly, patients with low PTH had a significantly higher serum Mg concentration than patients with adequate or high PTH (2.8 +/- 0.2 mg/dl vs 2.3 +/- 0.1 mg/dl and 2.2 +/- 0.1 mg/dl, respectively, p < 0.01). Moreover, regression analysis showed a negative linear correlation between serum PTH level and plasma Mg concentration (r = -0.6059, p < 0.001). Based on these findings, chronic hypermagnesemia could have a suppressive effect on PTH secretion, and it could be a risk factor for the development of adynamic bone disease in dialysis patients.

Maintenance Hemodialysis and Circulating Ionized Magnesium

“…It has been recently noted that in end-stage kidney disease chronically increased levels of total magnesium decrease parathyroid hormone levels and predispose to a dynamic bone disease [15, 16]. It has therefore been suggested to reduce the magnesium dialysate concentration at least in this peculiar situation [15, 16].…”

“…It has been recently noted that in end-stage kidney disease chronically increased levels of total magnesium decrease parathyroid hormone levels and predispose to a dynamic bone disease [15, 16]. It has therefore been suggested to reduce the magnesium dialysate concentration at least in this peculiar situation [15, 16]. The results of the present study confirm that the total and the free levels of magnesium often do not go hand in hand and demonstrate that in this condition the total concentration of magnesium mostly overestimates that of ionized magnesium, the most attractive form with respect to biological properties.…”

“…Evaluation of the plasma anion gap is useful in metabolic acidosis because an elevated anion gap points to the presence of unmeasured anions [15, 16, 17]. In order to make a more sound interpretation of the plasma anion gap, it is mandatory to correct it taking into consideration the prevailing levels of ‘minor cations’ such as total plasma magnesium (Mg, in mmol/l) and calcium (Ca, in mmol/l) in the following way [13]:…”

Causes and Consequences of Adynamic Bone Disease

“…(2)  Magnesium: Navarro et al noted a significant negative correlation between serum magnesium and PTH, both in hemodialysis [54, 55]and CAPD patients [56, 57]. Magnesium affects PTH in a similar way to calcium [58, 59].…”

Hypomagnesemia in Hemodialysis Patients: Role of Proton Pump Inhibitors

“…Several past studies have suggested that hypermagnesemia, by increasing total body and bone magnesium, may lead to worsening of renal osteodystrophy [4], delayed nerve conduction [5], and pruritus [6], and that lowering plasma [Mg] can improve these abnormalities [4,5,6]. More recently, use of magnesium as an inexpensive phosphate binder [7,8,9,10,11] and the possible role of high magnesium in adynamic bone disease [12] have led to use of a lower dialysate [Mg]. Whereas mild hypermagnesemia is expected with use of a dialysate [Mg] of 1.5 mEq/l [13,14,15,16], a dialysate [Mg] of 1.0 mEq/l has generally been associated with either normal plasma [Mg] or mild hypermagnesemia [17,18].…”