Incomplete renal tubular acidosis and bone mineral density: a population survey in an area of endemic renal tubular acidosis

Abstract

Background: 'Primary' osteoporosis has been associated with a high incidence of a renal acidification defect, incomplete renal tubular acidosis (iRTA). An acid loading test, to exclude the defect, has been recommended for inclusion in the work-up of osteoporosis. However, there is no community-based study to confirm its utility.

Method: A community-based survey was conducted in the Khon Kaen province, Thailand, between January and June, 2000. We randomly enrolled 361 apparently healthy adults, 146 men and 215 women, in this study. The bone mineral densities (BMDs) of the spine and femur were determined in all subjects. The diagnosis of iRTA was based on: normal serum electrolytes and one or both of first morning urinary pH >5.5 or the failure of an acid loading test to decrease it to >5.5. Dietary diaries, serum electrolyte tests and 24 h urine collections were obtained from all iRTA subjects.

Results: There were 23 (6.4%) iRTA subjects in the population studied. The age, height, weight and calcium intake were comparable between iRTA and normal subjects, as were the BMDs of spine and femur. There was no difference between the two groups in the distributions of BMD with age for either area. Multiple regression analyses of the studied population demonstrated that age, body weight, duration of menopause and gender (only for the femoral neck) were independent variables that affected BMD.

Conclusion: Incomplete distal renal tubular acidosis alone was not associated with lower bone mass in this cohort. It may nevertheless be valuable to monitor serum electrolytes and BMD in patients with iRTA due to their tendency to develop intermittent metabolic acidosis.