OBJECTIVE The etiology of osteoporosis in asthma is complex as various factors contribute to its pathogenesis. The purpose of our study was to investigate the effects of obesity and inhaled steroids, as well as the severity and duration of asthma, on osteoporosis in postmenopausal asthma patients as compared to healthy controls. METHODS A total of 46 patients with asthma and 60 healthy female controls, all postmenopausal, were enrolled in our study. Bone mineral density was assessed at the lumbar spine and hip using a Lunar DPX-L densitometer. RESULTS Bone mineral density (BMD) scores were comparable between the asthmatic and control groups, with average scores of 0.95 +/- 0.29 and 0.88 +/- 0.14 g/cm(2), respectively. Likewise, osteoporosis was diagnosed in a similar percentage of patients in the asthmatic (39.1%) and control (43.3%) groups. Bone fracture was identified in four patients with asthma (8.6%) and in six patients from the control group (10%). We could not detect any relationship between BMD and duration of asthma, asthma severity, inhaled steroids or body mass index (BMI). There was no difference between the two groups with respect to age or years since menopause. Although asthma patients were more likely to be overweight and presented higher BMD scores on average than the control subjects, these differences were not statistically significant. CONCLUSIONS There is a slight positive protective effect of high BMI against osteoporosis in asthma patients, but this effect is overcome by time and menopause status. Therefore, the protective effect of obesity against osteoporosis in asthma patients seems to not be significant.