Evidence for a particularly severe secondary hyperparathyroidism in analgesic abuse nephropathy

Ca metabolism was compared in two groups of patients with chronic interstitial nephritis: in 21 patients (analgesic abuse nephropathy (AAN) group), nephropathy was due to exposure for 5-50 years (mean 21.1) to phenacetin-containing analgesics, whereas in 21 other patients (controls) it was due to exposure for 1-80 years (mean 21.4; NS) to other causes. Patients were followed for 2.5 +/- 0.6 and 1.6 +/- 0.6 years, respectively (mean +/- SEM; NS). Blood Ca, P, protein, creatinine, alkaline phosphatase, parathyroid hormone (PTH), 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)2D) as well as arterial acid-base status and urinary excretion rate of Ca, P and creatinine were determined serially. Results were included only when P was maintained between 0.7 and 1.9 mmol/l. The range of creatinine levels studied was 95-1,600 mumol/l. No differences were found between the two groups with respect to creatinine clearance, blood P, protein, arterial pH and bicarbonate, and urinary excretion rates of Ca and P. Mean plasma Ca was significantly lower, and PTH was significantly higher in the AAN group than in the control group; mean plasma alkaline phosphatase activity was also significantly higher in the AAN group. In both groups Ca was negatively correlated with creatinine, but the slope of the regression line was steeper in the AAN group than in controls. The degree of hypocalcemia was related to the increase in plasma PTH and alkaline phosphatase, but not to the plasma level of 25(OH)D or 1,25(OH)2D.(ABSTRACT TRUNCATED AT 250 WORDS)