title: Response to an oral calcium load in nephrolithiasis patients with fluctuating parathyroid hormone and ionized calcium levels.
abstract: 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.
authors.affiliation: Departamento de Endocrinologia, Universidade Federal de São Paulo, São Paulo, SP, Brasil.
authors.forename: S A
authors.initials: SA
authors.lastname: Gomes
authors.forename: A
authors.initials: A
authors.lastname: Lage
authors.forename: M
authors.initials: M
authors.lastname: Lazaretti-Castro
authors.forename: J G H
authors.initials: JG
authors.lastname: Vieira
authors.forename: I P
authors.initials: IP
authors.lastname: Heilberg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D002118:Calcium / Q000097:blood / Q000652:urine; D005260:Female; D006801:Humans; D006934:Hypercalcemia / Q000150:complications / Q000175:diagnosis*; D006961:Hyperparathyroidism / Q000150:complications / Q000175:diagnosis* / Q000000981:diagnostic imaging; D007669:Kidney Calculi / Q000150:complications*; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D011877:Radionuclide Imaging; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D010281:Parathyroid Hormone; D002118:Calcium