Abstract
Several calcium supplements are currently available and many of them are marketed without proper comparison of the bioavailability of the actual preparations. The aim of the present trial was to evaluate and compare the acute changes in serum calcium (Ca) and parathyroid hormone (PTH) levels following the oral administration of a vehicle and of five calcium salts currently prescribed in Western Europe. No significant changes in serum Ca or PTH levels were observed after administration of the vehicle. All calcium salts induced significant increases in serum Ca and decreases in serum PTH compared to baseline values. Comparison of the six response curves revealed a significantly greater increase in serum Ca and a greater decrease in serum PTH after each of the calcium salts than observed after the vehicle. However, no statistically significant differences were observed between the different calcium salts for serum Ca increments. The decrease in serum PTH observed after administration of an ossein-hydroxyapatite complex was significantly less important than after the four other calcium salts, even if statistically different than after vehicle. When assessing the area under the curve (AUC) of PTH values, we observed that calcium carbonate and citrate induce a significantly greater decrease in serum PTH than the other calcium salts which are, however, statistically more active than the vehicle. Serum PTH is decreased under the lower limit of the normal range (10 pg/ml), between t60 and t120 for calcium carbonate and citrate and between t60 and t90 for calcium gluconolactate while the mean PTH values remain within the normal range throughout the study with calcium pidolate, the ossein-hydroxyapatite complex and the vehicle. In conclusion, all calcium preparations significantly increase serum calcium and decrease serum parathormone, compared to what is observed after oral intake of a vehicle. However, significant differences in suppression of parathormone are observed between the different calcium preparations and might be of importance for their clinical use.