No abstract

To determine the timing of peak bone mass and density, we conducted a cross-sectional study of bone mass measurements in 265 premenopausal Caucasian females, aged 8-50 yr. Bone mass and bone mineral density were measured using dual X-ray absorptiometry and single-photon absorptiometry at the spine (anteroposterior, lateral), proximal femur, radius shaft, distal forearm, and the whole body. Bone mass parameters were analyzed using a quadratic regression model and segmented regression models with quadratic-quadratic or quadratic-linear form. The results show that most of the bone mass at multiple skeletal locations will be accumulated by late adolescence. This is particularly notable for bone mineral density of the proximal femur and the vertebral body. Bone mass of the other regions of interest is either no different in women between the age of 18 yr and the menopause or it is maximal in 50-yr-old women, indicating slow but permanent bone accumulation continuing at some sites up to the time of menopause. This gain in bone mass in premenopausal adult women is probably the result ofcontinuous periosteal expansion with age. Since rapid skeletal mineral acquisition at all sites occurs relatively early in life, the exogenous factors which might optimize peak bone mass need to be more precisely identified and characterized. (J. Clin. Invest.

Although boys with Duchenne muscular dystrophy on long-term corticosteroid treatment have a significantly decreased risk of scoliosis and an extension of more than 3 years' independent ambulation, they are at increased risk of vertebral and lower limb fractures compared with untreated boys.

Bone status and fracture rates were evaluated in two Yugoslav populations with very different dietary habits. In district A (Podravina) the daily calcium intake was about twice that in district B (Istra). There were similar but smaller differences in the intakes of other nutrients. In district B metacarpal cortical width was reduced in all age groups of both sexes but the difference tended to decrease with age. The proximal femur fracture rate was higher in district B than district A but there was no difference between the forearm fracture rates in the two districts. Our results confirm that bone mass at any age is clearly the result of age and sex and most probably other genetically determined factors but also show that this expression is nutrition related. The data suggest that nutrition (in particular the calcium intake) is an important determinant of bone mass in young adults but seems to have little effect on age-related bone loss in either males or females. The main determinant of cortical bone mass in the elderly seems to be the cortical bone mass in middle life. The proximal femur fractures of old people reflect declining cortical bone mass but the distal forearm fractures of middle-aged women are unrelated to cortical bone mass or nutritional status.

We suggested that calcium may be an important determinant of peak bone mass. For further elucidation, calcium balances in adolescent females with different calcium intakes (270-1637 mg/d), and a 2-y intervention study of calcium supplementation were performed. Hereditary influences on bone status were also evaluated by comparing subjects' and parents' bone mass. The main determinant of calcium balance was calcium intake; net calcium absorption increased with intake and urinary calcium did not change. Adolescent females retained 200-500 mg Ca/d, suggesting that inadequate calcium intake may translate into inadequate calcium retention and a reduction in peak bone mass. There was a more pronounced increase in bone mass over time in the calcium-supplemented group (1640 mg Ca/d) than in the control group (750 mg Ca/d), but the differences between bone mass measurements were not statistically significant, possibly because of a type II error. By the age of 16 y daughters had accumulated 90-97% of the bone mass of their premenopausal mothers.