Background: Few studies have been done of bone densities in humans receiving retinoids, despite a substantial amount of literature concerning retinoid-induced osteoporosis in animals. We prospectively measured bone density and calcium metabolism in young men (aged 17-25 years) receiving oral isotretinoin for cystic acne and in a group of healthy volunteers (aged 19- 26 years). Observations: Compared with that in healthy control subjects, mean bone density was lower at all sites (spine, femoral neck, and Ward triangle) and was considerably more variable at the spine in young men with cystic acne even before treatment. Bone density at the Ward triangle decreased a mean of 4.4% (P = .03) after 6 months of isotretinoin use (1 mg/kg of body weight). Four patients showed decreased density of more than 9% at the Ward triangle. The difference between the mean change in bone density in the patient group and in the control group was significant at the Ward triangle (P = .04) but not at the other sites. Measurements of calcium metabolism did not change over time in either group. Conclusions: A loss of bone density occurring in the absence of measurable alterations of calcium metabolism is likely to be a direct effect of retinoids on bone. Further study of retinoid-induced osteoporosis in humans and of bone density in patients with cystic acne is needed.
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