RESUMO
Patients with primary hyperparathyroidism have increased bone turnover, but it is less well documented how brief periods of excess parathyroid hormone (PTH) (endogenous or exogenous) affect bone metabolism. In the present double blind study, we examined the effect of either ethylenediaminetetraacetatic acid (EDTA) or placebo on serum levels of PTH and biochemical markers of bone turnover in 15 women and 39 men (aged 41 to 81 years) suffering intermittent claudication due to atherosclerosis. Disodium EDTA was administered as 20 repeated infusions of 3 grams during a period of 5-9 weeks. Serum calcium and serum phosphate decreased following treatment (p < 0.001) and remained unchanged in the placebo group. However, the differences between the groups were insignificant (ANOVA p = 0.13 and p < 0.10, respectively). PTH increased 2 1/2 fold following EDTA treatment (p < 0.001, ANOVA). The change in serum PTH was inversely correlated with the change in serum calcium (r = -0.53, p < 0.01). In the EDTA group, urinary hydroxyproline/creatinine and calcium/creatinine increased after treatment (ANOVA p < 0.001 and p < 0.05, respectively). Serum bone alkaline phosphatase decreased significantly in the EDTA group immediately after treatment (p < 0.001, ANOVA) and returned to baseline level at three months while only an insignificant decrease in serum osteocalcin was seen following treatment. We conclude that EDTA treatment increases endogenous PTH secretion considerably and leads to increased bone resorption. However, no changes in osteoblastic markers indicating increased activation of bone remodeling could be demonstrated. Our findings support that chelation therapy with EDTA is accompanied by bone loss.