Effect of calcium supplementation on blood pressure in patients with secondary hyperparathyroidism

The aim was to study the effect of calcium supplementation 477 mg twice daily on BP in patients with secondary hyperparathyroidism during an intervention study (6 weeks) and after 954 mg during a short study (3 h). The intervention study was a placebo-controlled, double-blind, cross-over, while the short study gave a placebo and calcium in random order on separate days. The participants were obtained from an epidemiological survey in Tromsø 1994-1995 that included more than 27.000 subjects. The re-examination was performed in 2000/2001 at the University Hospital of North Norway, Norway. There were 18 subjects with secondary hyperparathyroidism and 28 control subjects in the intervention study while there were 14 cases and 8 control subjects in the short study. The results showed that in the subjects with secondary hyperparathyroidism after calcium supplementation in the intervention study there was an increase in serum calcium from 2.28 +/- 0.09 to 2.36 +/- 0.06 mmol/l (mean +/- SD) and a decrease in serum PTH from 8.6+/-1.6 to 6.5+/-2.4 pmol/l. However, there was no significant difference in either systolic or diastolic BP between calcium supplementation and placebo (138.3 +/- 21.0 vs 135.9 +/- 17.0 mm Hg and 80.9 +/- 11.1 vs 78.9+/-9.5 mm Hg, respectively). Similar results were seen in the control group. In the short study, serum calcium increased and serum PTH decreased after oral calcium, but the BP did not differ as compared to when placebo was given. To conclude, in the present setting we did not find any effect on BP by calcium supplementation in subjects with moderate secondary hyperparathyroidism.