Determination of bone mineral content (BMC) by dual photon absorptiometry: Age-, sex-, and menopause-related changes in Bavaria and effect of estrogen replacement in early postmenopausal women

Cortical (neck of femur) and trabecular bone mass (L2-4) have been determined repeatedly with DPA using GD 153 (NOVO Lab 22 a) in 545 female and 112 male pts with no evidence of bone diseases. Measured 'normal', (age- and sex-related average) BMC values differed significantly from those of US people determined by same equipment, i.e., were in average about 30% lower, but matched well with corresponding results from Belgium. BMC-area was found the most suitable parameter both for cross-sectional and longitudinal studies, since BMC-area is independent from height and weight. But there is still need to reduce the overlap and improve accuracy and reproducibility for making decisions after shorter intervals. Assessment of the individual mineral loss and fracture risk by comparing to average values, however, remains problematic due to the wide range of 'normal' BMC and in women additionally due to the variable onset of menopause. For estimations of the individual fracture risk of elderly pts BMC should not be normalized on age, because at the age of 65 half of the women had 'pathologic' values, i.e. were below the so called 'osteoporosis threshold'. Comparison of the individually measured postmenopausal BMC to average values of premenopausal women and to BMC values normalized to their menopausal age may be helpful approaches for overcoming these difficulties. Because of the lack of earlier individual data in most cases repeated BMC measurements are still required for assessment of demineralization speed. Preliminary results of estrogen replacement therapy with low doses of natural conjugated estrogen show good prevention of bone loss in healthy but not in ovarectomized women. (orig./MG)