REPRODUCTIVE DEVELOPMENT &BONE ACCRETION IN YOUNG WOMEN

Project: Research project

Project Details

Description

The major goal of the proposed research is to investigate the determinants
of bone dynamics in young women in order to develop strategies to prevent
osteoporosis. Recent studies have confirmed that 1) peak bone density is
a predictor of osteoporosis risk; 2) 50% of adult bone mass in females is
acquired during adolescence; and 3) for most women, 95% of adult peak bone
mass is achieved near the age of 20. The present study (in the first award
period) was designed such that he cohort was homogeneous at entry at age 12
with respect to age, race, and pubertal development. BMI and baseline bone
density values were used to balance the study groups with respect to
genetic influences on bone. In this study, we used a randomized double-
blind, placebo-controlled trial and determined that calcium supplementation
of 350 mg/d calcium from calcium citrate malate initiated at either age 12
or at age 14 produces a 1.5% annualized increase (p=0.005) in normal bone
gain. This increase, if continued for three years and maintained to peak
bone mass, should lead to a significant reduction in risk of future
osteoporotic fractures. We evaluated the interrelationships among physical
activity, physical fitness, nutrient intake, pubertal progression and bone
development in girls from age 12 through age 15 and determined that among
well-nourished girls cumulative estrogen exposure and dietary calcium
intake are the most powerful determinants of bone gain during early and
mid-adolescence.

We propose to continue to study the subjects from age 16-21 and to
determine how dietary, endocrine and lifestyle factors affect bone dynamics
and acquisition of peak bone mass. Of the 112 original volunteers, 90
remain in the present cohort and of these 89 (00%) are interested in
remaining in the study. During the next 5 years, subjects will not receive
calcium supplement or placebo pills;' and we will 1) Determine whether the
increase in bone gain due to calcium supplementation from age 12 or from
age 14 results increase in adult bone mass; 2) Determine how late
adolescent bone gain is related to--a) cumulative adolescent dietary
calcium intake; b) physical activity and physical fitness patterns; c)
urinary collagen cross-link excretion; d) changes in body composition and
anthropometric variables; and e) late adolescent and early adult
reproductive hormone levels; 3) Quantify the effect of adolescent
menstrual history, cumulative estrogen exposure and cumulative calcium
intake on peak bone mass. Continuation of the longitudinal study design is
essential to answering these questions. Each subject will be seen yearly.
Comprehensive bone and body composition measurements will be made by dual
energy x-ray absorptiometry (DEXA). We will also obtain medical and
menstrual histories, anthropometric measurements, reproductive hormone
measurement from serum samples, nutrient analyses from three day diet
records, physical activity assessed by questionnaire, physical fitness
measured by cycle ergometry, and bone-specific collagen crosslink excretion
measured from urine specimens. The findings from this study will lead to
a grater understanding of how modifiable life style factors affect peak
bone mass dynamics. Such knowledge is essential to the development of bone
health promotion strategies for young American women.
StatusFinished
Effective start/end date1/1/9011/30/00

Funding

  • Eunice Kennedy Shriver National Institute of Child Health and Human Development
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development

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