Response to an oral calcium load in nephrolithiasis patients with fluctuating parathyroid hormone and ionized calcium levels

• Published in: Brazilian journal of medical and biological research 2004-09, Vol.37 (9), p.1379-1388
• Main Authors: Gomes, S A, Lage, A, Lazaretti-Castro, M, Vieira, J G H, Heilberg, I P
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aged, 80 and over; BIOLOGY; Bone Density; Bone mineral density; Calcium; Calcium - blood; Calcium - urine; Female; Humans; Hypercalcemia - complications; Hypercalcemia - diagnosis; Hypercalciuria; Hyperparathyroidism; Hyperparathyroidism - complications; Hyperparathyroidism - diagnosis; Hyperparathyroidism - diagnostic imaging; Kidney Calculi - complications; Male; MEDICINE, RESEARCH & EXPERIMENTAL; Middle Aged; Nephrolithiasis; Parathyroid hormone; Parathyroid Hormone - blood; Radionuclide Imaging; Sensitivity and Specificity; Time Factors
• ISSN: 0100-879X; 1414-431X; 0100-879X; 0034-7310
• DOI: 10.1590/S0100-879X2004000900013

The response to an oral calcium load test was assessed in 17 hypercalciuric nephrolithiasis patients who presented elevated parathyroid hormone (PTH) irrespective of the ionized calcium (sCa2+) levels. Blood samples were collected at baseline (0 min) and at 60 and 180 min after 1 g calcium load for serum PTH, total calcium, sCa2+, and 1.25(OH)2D3 determinations. According to the sCa2+ level at baseline, patients were classified as normocalcemic (N = 9) or hypercalcemic (N = 8). Six healthy subjects were also evaluated as controls. Bone mineral density was reduced in 14/17 patients. In the normocalcemic group, mean PTH levels at 0, 60 and 180 min (95 +/- 76, 56 +/- 40, 57 +/- 45 pg/ml, respectively) did not differ from the hypercalcemic group (130 +/- 75, 68 +/- 35, 80 +/- 33 pg/ml) but were significantly higher compared to healthy subjects despite a similar elevation in sCa2+ after 60 and 180 min vs baseline in all 3 groups. Mean total calcium and 1.25(OH)2D3 were similar in the 3 groups. Additionally, we observed that 5 of 9 normocalcemic patients presented a significantly higher concentration-time curve for serum PTH (AUC0',60',180') than the other 4 patients and the healthy subjects, suggesting a primary parathyroid dysfunction. These data suggest that the individual response to an oral calcium load test may be a valuable dynamic tool to disclose a subtle primary hyperparathyroidism in patients with high PTH and fluctuating sCa2+ levels, avoiding repeated measurements of both parameters.