Differential effects of thiazide and estrogen upon bone mineral content and fracture prevalence.

Individual and combined effects of thiazides and estrogens upon bone mineral content at four sites (proximal radius, distal radius, os calcis, lumbar spine) and fracture prevalence were assessed retrospectively in 993 postmenopausal women. Compared with untreated women, use of thiazide alone was associated with significantly higher bone mineral content (P less than or equal to .01); nonspine fracture prevalence in this group was reduced by one-half (P = .07). Estrogen alone also was associated with significantly higher bone mineral content (P less than or equal to .0001); nonspine fracture prevalence was reduced by almost one-half (P = .07). The users of both estrogen and thiazide had the highest bone mineral content levels, which were significantly different than the thiazide-only group at four bone sites (P less than or equal to .001), and the estrogen-only group for three bone sites (P less than or equal to .05). Nonspine fracture prevalence for the users of both drugs was 17% that of the untreated group (P = .02). The relationships with spine fracture prevalence were less consistent; however, estrogen users appeared to have a lower spine fracture prevalence rate and higher spinal bone mineral content than thiazide users. These findings suggest a potential role for thiazides in the prevention of osteoporosis.