[Alterations in calcium metabolism in patients with active tuberculosis]

Abnormalities in phosphocalcic and vitamin D metabolism may develop in patients with active tuberculosis (TB). Their incidence and relationship with the disease is not well known, particularly in our area. We have prospectively evaluated 40 patients with TB [(30 with localized TB (LTB) and 10 with disseminated TB (DTB)].

After stabilizing the diet during 4 days, the calcium, phosphorus, magnesium and creatinine balances, blood ionic calcium, plasma intact PTH, 25-hydroxy vitamin D [25(OH)D] and serum 1.25 dihydroxyvitamin D [1.25(OH)2D] were measured.

Hypercalcemia was not found in any patient, but 25% had hypercalciuria (HC). The 24-hour urinary excretion of calcium was higher in patients than in controls (3.2 +/- 1.7 mg/kg or 0.10 +/- 0.06 mg/100 ml of GFR vs 2.3 +/- 0.7 mg/kg or 0.08 +/- 0.03 mg/100 ml of GFR, p less than 0.05), basically at the expense of patients with DTB (4.4 +/- 1.8 mg/kg or 0.14 +/- 0.06 mg/10 ml of GFR, p less than 0.005). These had a lower PTH than patients with LTB and controls (12.8 +/- 7.7 vs 18.5 +/- 6.9 vs 19.5 +/- 6.0 pg/ml, p less than 0.05). Independently from the extent of the disease, the patients with HC had a lower PTH (12.6 +/- 6.8 vs 18.5 +/- 6.9 pg/ml, p less than 0.01) and higher serum 1.25(OH)2D (34.5 +/- 10.1 vs 25.0 +/- 7.2 pg/ml, p less than 0.01) than patients without HC. The levels of 25(OH)D were lower in patients with TB than in controls (11.2 +/- 6.0 vs 20.0 +/- 7.0 ng/ml, p less than 0.05), independently from the extent of the disease and the presence or absence of HC.

Patients with tuberculosis may have hypercalcinuria with inadequately high levels of 1.25(OH)2D and low intact PTH. This abnormality appears to be correlated with the extent of the disease.