Using constant infusions of [3H]androgen/[14C]estrogen we measured metabolic clearance and production rates and aromatization of androgens to estrogens in post-menopausal women with vertebral crush fractures and compared these results to similar measurements in a similar population of post-menopausal women who did not have vertebral crush fractures. The mean +/- SEM values for the metabolic clearance rates of testosterone and estrone, 220 +/- 10 and 880 +/- 50 1/day per m2, were significantly less in the crush fracture group than the respective mean values in the control group, 280 +/- 15 and 1110 +/- 70 1/day per m2. The mean concentration of estradiol was higher in the crush fracture group, 18 +/- 2 pg/ml, compared to that in the control group, 13 +/- 1 pg/ml. However, for the crush fracture group the mean blood production rates of both androstenedione, 0.7 +/- 0.1 mg/day, and testosterone, 56 +/- 9 micrograms/day, were significantly less than the respective values in the control group, 1.2 +/- 0.2 mg/day and 115 +/- 15 micrograms/day. The production rates for estrone and estradiol were not different for the two groups. In addition the mean value for the fraction of adrostenedione converted to testosterone ( [rho]A, T BB) was lower in the crush fracture, 0.030 +/- 0.002 compared to the control group, 0.041 +/- 0.004. Thus the amount of biologically available androgen is less in the vertebral crush fracture group than in the control group. However, since these measurements represent an isolated point temporally removed from major changes in bone morphology, their exact relationship to the crush fracture and osteoporotic process remains uncertain.