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.