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We thank Dr. Kamel for his comments on our recently published study of the effect of thiazide diuretics on normal postmenopausal bone loss ( 1 Reid I.R. Ames R.W. Orr-Walker B.J. et al. Hydrochlorothiazide reduces loss of cortical bone in normal postmenopausal women a randomized controlled trial. Am J Med. 2000; 109: 362-370 Abstract Full Text Full Text PDF PubMed Scopus (161) Google Scholar ). In general, we agree with his conclusions but have some further minor comments. Changes in renal tubular absorption of calcium probably contribute to the increase in urine calcium after the menopause, as does the nearly twofold increase in the rate of bone resorption that also occurs then. Dr. Kamel comments that calcium supplements “restore serum calcium levels.” That is not really correct, as serum calcium levels are higher in postmenopausal women than in premenopausal women, and the effect of serum calcium supplementation is to suppress parathyroid hormone and bone resorption, rather than to change serum calcium levels themselves ( 2 Reid I.R. Ames R.W. Evans M.C. et al. Effect of calcium supplementation on bone loss in postmenopausal women. N Engl J Med. 1993; 328: 460-464 Crossref PubMed Scopus (448) Google Scholar ). He repeats the long-held view that the actions of thiazides on bone are principally by way of changing tubular resorption of calcium. That is likely to be substantially true, although a significant finding of our recent study was that thiazides might also directly inhibit bone resorption, possibly through their known inhibition of carbonic anhydrase in the osteoclast ( 1 Reid I.R. Ames R.W. Orr-Walker B.J. et al. Hydrochlorothiazide reduces loss of cortical bone in normal postmenopausal women a randomized controlled trial. Am J Med. 2000; 109: 362-370 Abstract Full Text Full Text PDF PubMed Scopus (161) Google Scholar ). Dr. Kamel concludes that thiazides should be preferentially given to women with high urine calcium excretion. It should be noted, however, that in our study, the size of the therapeutic benefit was not related to the baseline urine calcium excretion. The key finding of our study—that thiazides produce small but detectable beneficial effects on bone density—has recently been supported by data from a similar study by LaCroix et al ( 3 LaCroix A.Z. Ott S.M. Ichikawa L. Scholes D. et al. Low-dose hydrochlorothiazide and preservation of bone mineral density in older adults. A randomized, double-blind, placebo-controlled trial. Ann Intern Med. 2000; 133: 516-526 Crossref PubMed Scopus (185) Google Scholar ). Dr. Kamel is probably correct in concluding that the principal relevance of these trials is to the selection of antihypertensive therapy for postmenopausal women, as there are obviously much more potent agents that can be used to increase bone density in women with osteoporosis. What role would thiazide diuretics have in the prevention of postmenopausal osteoporosis?The American Journal of MedicineVol. 111Issue 2Preview Full-Text PDF