It is generally believed that glucocorticoids cause osteoporosis through a combination of decreased bone formation and increased bone resorption. However, the direct effect of glucocorticoids on osteoclasts has not been determined. We therefore tested the effects of hydrocortisone and dexamethasone on bone resorption by osteoclasts disaggregated from neonatal rat long bones. Hydrocortisone and dexamethasone caused a dose-dependent inhibition of osteoclastic bone resorption in the range 10(-7) to 10(-5) M, and 10(-9) to 10(-6) M, respectively, at concentrations likely to occur during therapy and disease. Inhibition of bone resorption was found to be associated with impaired osteoclast survival: osteoclast numbers were reduced to approximately 25% of control values by 10(-6) M hydrocortisone and 10(-7) M dexamethasone. Osteoclast cytotoxicity by glucocorticoids was completely antagonized by progesterone, which itself had no effect on osteoclast survival. Analysis of the time course of these inhibitory effects showed a nonsignificant reduction in survival by 6 h and marked inhibition of survival by 12 h. We could detect no specific changes in osteoclast morphology in association with this impaired viability. The relative potencies of the glucocorticoids for impairment of osteoclast viability was similar to their relative affinities for binding the glucocorticoid receptor, and this, together with inhibition by progesterone, suggests a receptor-mediated mechanism. Such a receptor-mediated cytotoxic action of glucocorticoids has only previously been reported with lymphoid cells. The sensitivity of osteoclasts to the lethal effects of glucocorticoids suggests that glucocorticoids may have a role in physiology as inhibitors of osteoclastic bone resorption.

1. We analysed the lumbar spine (L2-L4) and femoral neck bone mineral density results of Caucasian (n = 2232), Asian (Indian sub-continent) (n = 153) and Afro-Caribbean (n = 102) women referred for bone densitometry over a 30 month period. To assess the risk of osteoporosis, the results of Caucasian and Asian women were compared with those of a reference Caucasian population supplied by Lunar. 2. Subject characteristics were similar in all three groups, other than expected ethnic differences in stature and weight. We found that lumbar spine and femoral neck bone mineral density in Caucasians was lower than in Afro-Caribbeans, but higher than in Asians. Consistent with this, bone mineral density was also lower in Asians as compared with the reference Caucasian population, both at the lumbar spine and femoral neck. As a consequence, a higher proportion of Asian women were classified as being at increased risk of osteoporosis than Caucasian women. 3. Since ethnic differences in skeletal size might influence bone mineral density, we also obtained values for bone mineral content in Caucasian and Asian women that were corrected for projected skeletal area, and weight and years since menopause, using regression equations derived from the Caucasian study population. After this analysis, the difference in bone mineral content between Caucasians and Asians at the lumbar spine disappeared, while that at the femoral neck persisted. 4. We conclude that the assessment of risk of osteoporosis in Asian women by comparing bone mineral density with a reference Caucasian population may have limited validity because of the influence of skeletal size on such measurements.

Bone mineral density (BMD) was evaluated by dual energy x ray absorptiometry in 60 adults (33 males, 27 females; aged 50, range 23-76 years) who were growth hormone deficient from various causes for 10-4 (1-31) years. Adult patients who had acquired growth hormone deficiency before completion of puberty had significantly reduced mean (SEM) BMD compared with age matched healthy controls at the lumbar spine: 0-87 (0.09) v 1-20 (0.03) g/cm2, femoral neck: 0-81 (0-06) v 1-08 (0.04) g/cm2, and Ward's triangle: 0-68 (0.07) v 1-04 (0.05) g/cm2. These values were also reduced compared with those of patients who had received human growth hormone during puberty. Untreated growth hormone deficiency when present during puberty results in reduced adult bone density.

Although radiological studies suggest that Marfan syndrome is associated with osteopenia, investigations utilizing measurements of bone mass have yielded conflicting results. To address this question further, we measured bone mineral density (BMD) in 14 women with Marfan syndrome at the right hip and lumbar spine by dual energy X-ray absorptiometry (DXA). Results were compared with the age- and weight-matched reference population supplied by the DXA manufacturer, and with our own control population of normal women, the latter being matched for height, in addition to age and weight. We found that BMD was very similar in our Marfan women as compared with the two reference populations, at the lumbar spine and femoral neck, while trochanteric BMD was reduced. However, the relationship between an isolated reduction in trochanteric BMD and future fracture risk is unclear, and, on the basis of our results, we conclude that Marfan syndrome is not associated with a clinically significant increase in the risk of osteoporotic fracture.