Cholecalciferol supplementation improves secondary hyperparathyroidism control in hemodialysis patients

Abstract

Introduction: Vitamin D deficiency is common among hemodialysis (HD) patients and is an important component in the pathogenesis of secondary hyperparathyroidism (SHPT). We herein report our experience on the impact of cholecalciferol supplementation on PTH levels in a group of HD patients.

Patients and methods: We selected 122 HD patients. The main selection criteria were 25-hydroxyvitamin D (25(OH)D) levels ≤30 ng/mL and SHPT defined as PTH levels >300 pg/mL or PTH levels between 150-300 pg/mL during therapy with cinacalcet or paricalcitol. 82 patients agreed to receive cholecalciferol at the fixed dose of 25,000 IU per week orally for 12 months, while the remaining 40 represented the control group. The main endopoints of the study were the reduction in PTH levels ≥30% compared to baseline values and the increase of 25(OH)D levels to values >30 ng/mL.

Results: At follow-up PTH levels decreased in the supplemented group from 476 ±293 to 296 ± 207 pg/mL (p<0.001), 25(OH)D levels increased from 10.3 ± 5.7 to 33.5 ± 11.2 ng/mL (p<0.001), serum calcium increased from 8.6 ± 0.5 to 8.8 ± 0.6 mg/dL (p<0.05) while serum phosphorus did not change. In this group the mean doses of paricalcitol were significantly reduced, from 8.7 ± 4.0 to 6.1 ± 3.9 µg/week (p<0.001). Moreover, in this group there were a significant increase of hemoglobin levels, from 11.6 ± 1.3 to 12.2 ± 1.1 g/dL (p <0.01) and a significant reduction of erythropoietin doses (p<0.05). In the control group the 25(OH)D and PTH levels did not change, while cinacalcet doses increased from 21 ±14 to 43 ± 17 mg/d (p<0.01).

Conclusions: Vitamin deficiency is very common in HD patients. Cholecalciferol treatment significantly increased serum 25(OH)D levels, significantly decreased PTH levels and paricalcitol doses, concurrently entailing a better control of anemia. 

Keywords: vitamin D, cholecalciferol, hemodialysis, secondary hyperparathyroidism, paricalcitol

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Introduzione

L’iperparatiroidismo secondario (IPS) inizia come un processo adattativo ma in ultimo, a seguito del ridursi della funzione renale, della ridotta escrezione di fosfati, della ridotta produzione di vitamina D e dell’ipocalcemia, si trasforma in un processo patologico [1]. È opinione comune che bassi livelli sierici di vitamina D siano la causa del bilancio negativo del calcio, dell’IPS e della patologia ossea. Le concentrazioni sieriche di 25-idrossivitamina D (25(OH)D) sono il principale indice del patrimonio di vitamina D del nostro organismo e sono utilizzate per definire uno stato carenziale di vitamina D [2]. Nelle linee guida National Kidney Foundation–Kidney Disease Outcomes Quality Initiative (NKF–KDOQI), livelli sierici di 25(OH)D <5 ng/mL sono utilizzati per indicare una grave deficienza di vitamina D, livelli tra 5 e 15 ng/mL indicano una lieve insufficienza, livelli tra 16 e 30 ng/mL indicano un’insufficienza, mentre livelli maggiori di 30 ng/mL vengono considerati ottimali, anche se non vi è unanime consenso su quali siano i livelli sierici di vitamina D da considerare ottimali [3, 4].

 

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Metabolic effects of Cholecalciferol supplementation in kidney stone formers with vitamin D deficiency

Abstract

Introduction. In this paper we investigated whether cholecalciferol supplementation, prescribed to treat vitamin D deficiency in patients with nephrolithiasis, increased the risk of stone recurrence.

Methods. Calcium excretion and urine supersaturation with calcium oxalate (ßCaOx) and brushite (ßbsh) were evaluated in 33 kidney stone formers (aged 56±17; 12 males), both before and after therapy with cholecalciferol, prescribed as oral bolus of 100.000-200.000 UI, followed by maintenance doses, repeated every week (5.000-10.000 UI) or month (25.000-50.000 UI). During the study, patients followed a dietary regimen which included a daily calcium intake of about 800-1000 mg.

Results. Urinary nitrogen, sodium and ash-acid excretion did not significantly change during the study. After cholecalciferol supplementation, the main results were as follows: both serum calcium and phosphate did not vary significantly; 25(OH)VitD3 increased from 11,8±5,5 to 40,2±12,2 ng/mL (p<0,01); 1,25(OH)2 VitD3 increased from 41,6±17,6 to 54,0±16,0 pg/mL (p<0,01); PTH decreased from 75,0±27,2 to 56,7±21,1 pg/mL (p<0,01); daily urinary calcium increased from 2,7±1,5 to 3,6±1,6 mg/Kg b.w. (p<0,01), whereas fasting urinary calcium did not change significantly. After therapy, ßbsh increased from 0,9±0,7 to 1,3±1,3 (p=0,02) and ßCaOx did not vary significantly. Before cholecalciferol supplementation, 6/33 patients (18.2%) were hypercalciuric, whereas 13/33 patients (39,4%) showed hypercalciuria after supplementation (pX2=0,03).

Conclusions. Cholecalciferol supplementation for vitamin D deficiency may increase both urinary calcium and urine supersaturation in stone formers. If vitamin D supplements are needed in these patients, a careful monitoring of urine metabolic profile is warranted, in order to customize the metaphylaxis accordingly (hydration, potassium citrate, thiazides).

 

Keywords: Vitamin D deficiency, Cholecalciferol, Nephrolithiasis, Urolithiasis, Hypercalciuria

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INTRODUZIONE

 La carenza di vitamina D è oggi diffusa, non soltanto fra i soggetti a rischio, quali ad esempio le persone anziane, con scarsa esposizione alla luce solare, obese o affette da patologie gastroenteriche con malassorbimento (1,2), ma anche fra gli individui giovani, attivi e in buone condizioni generali quali sono molti pazienti affetti da calcolosi renale (35). A riguardo di questi ultimi, sussistono alcuni peculiari aspetti metabolici meritevoli di essere considerati.

 

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