A study of calcium and vitamin D metabolism in Chinese patients with pulmonary tuberculosis.

Hypercalcaemia can occur in patients with tuberculosis. To further characterize the calcium and vitamin D metabolism in this disorder, serum calcium, 25(OH)D, 1,25(OH)2D and parathyroid hormone and the interrelationships between serum calcium, 25(OH)D and 1,25(OH)2D were compared in 24 untreated Chinese patients with culture-positive pulmonary tuberculosis and 24 age and sex-matched controls in Hong Kong. Albumin adjusted serum calcium was significantly higher in patients (2.33 +/- 0.07 compared with 2.20 +/- 0.09 mmol l-1, P < 0.001), despite a lower calcium intake (426 +/- 208 compared with 564 +/- 335 mg day-1). No significant group difference was found in serum 25(OH)D or 1,25(OH)2D concentrations. There was a positive correlation between serum 25(OH)D and 1,25(OH)2D concentrations in the patient group (r = 0.50, P < 0.02), but a negative one in the control group (r = -0.48, P < 0.05). Serum parathyroid hormone was significantly lower in patients (20.9 +/- 8.5 compared with 38.2 +/- 14.5 pmol l-1, P < 0.001). In the patient group, no correlation between the radiographic extent of disease and serum calcium or 1,25(OH)2D concentrations was seen. Our findings confirmed that serum calcium is raised in tuberculosis but the effect may be reduced by a low calcium intake and a low parathyroid hormone level. Although the calcium and vitamin D metabolism appeared to be altered in tuberculosis, no direct relationship between serum calcium and 1,25(OH)2D, was found.