Calcium citrate versus calcium carbonate in the management of chronic hypoparathyroidism: a randomised, double-blind, crossover clinical trial

: In hypoparathyroidism (HypoPT), calcium supplementation is virtually always required although the disease is likely to be associated with an increased risk of nephrolithiasis. The use of calcium citrate (Ca-Cit) theoretically could have a positive impact on the nephrolithiasis risk because citrate salts are used to reduce this risk. To evaluate the potential therapeutic advantage of Ca-Cit in comparison with calcium carbonate (CaCO3 ) in HypoPT, on nephrolithiasis risk factors as well as to their ability to maintain desirable serum calcium levels. We also evaluated these preparations on quality of life (QOL). This randomised, double-blind, crossover trial recruited 24 adults with postsurgical chronic hypoparathyroidism at Campus Bio-Medico University of Rome. Participants were randomized 1:1 to Ca-Cit or CaCO3 for one month and then crossed-over to the other treatment for another month. The primary outcomes were changes in albumin-adjusted serum calcium and in ion activity product of calcium oxalate levels [AP(CaOx)index]. Secondary efficacy outcomes included changes in SF-36 survey score, fatigue score, constipation, and adverse events. No difference in terms of AP(CaOx)index was observed between the two groups. However, Ca-Cit was associated with a significant reduction in the oxalate/creatinine ratio compared to CaCO3 [-2.46 mmol/mol(SD 11.93) vs 7.42 mmol/mol(SD 17.63), p = 0.029]. Serum calcium and phosphorus concentration was not different between the two calcium preparations. Ca-Cit was associated with less constipation(p = 0.047). No difference was found in QOL scores. Although Ca-Cit did not modify the AP(CaOx)index when compared to CaCO3, it was associated with a reduction in urinary oxalate excretion that could have a potential beneficial effect on nephrolithiasis risk. These results are likely to have clinical implications in HypoPT, particularly those who do not tolerate CaCO3 and those affected by nephrolithiasis. A longer-term experience is needed to confirm these findings. This article is protected by copyright. All rights reserved.