High ratio of 1,25-dihydroxyvitamin D(3) to parathyroid hormone in serum of tuberculous patients with end-stage renal-disease

Aim: Diagnosis of tuberculosis is sometimes difficult because of the low specificity of diagnostic procedures especially in patients on end-stage renal disease (ESRD). As abnormal vitamin D metabolism has been reported in tuberculosis, the aim of the present study was to determine whether serum concentration of 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) may be a useful diagnostic indicator of tuberculosis in patients with ESRD. Patients and methods: Serum concentrations of 1,25-(OH)(2)D(3), parathyroid hormone (PTH), and calcium were compared in 6 patients with ESRD and active tuberculosis (ESRD-TB group) and 110 patients with ESRD and no tuberculosis (ESRD group). These parameters were compared before and after treatment for tuberculosis in patients of ESRD-TB group. Results: Hypercalcemia was observed in all 6 patients in the ESRD-TB group. Both higher serum concentration of 1,25-(OH)(2)D(3) and lower serum concentration of PTH were observed in the ESRD-TB group relative to the ESRD group, suggesting enhanced extrarenal production of 1,25(OH)(2)D(3) and suppressed secretion of PTH by hypercalcemia in the ESRD-TB group. However, these parameters could not be used to distinguish the ESRD-TB group from the ESRD group. The ratio of 1,25-(OH)2D3 to PTH in serum was above 0.9 in the ESRD-TB group and below 0.9 in the ESRD group. Antituberculous treatment reduced this ratio to the range observed in the ESRD group. Conclusion: High ratio of 1,25-(OH)2D3 to PTH in serum is noted in active tuberculous patients with ESRD because of enhanced extrarenal production of 1,25-(OH)(2)D(3).