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      Effect of puberty on body composition.

      Current Opinion in Endocrinology, Diabetes, and Obesity

      Absorptiometry, Photon, Adipokines, physiology, Adipose Tissue, anatomy & histology, Adolescent, Body Composition, Bone Density, Child, Female, Humans, Magnetic Resonance Imaging, Male, Models, Biological, Plethysmography, Puberty, Sex Characteristics, Young Adult

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          Abstract

          Here we examine the effect of puberty on components of human body composition, including adiposity (total body fat, percentage body fat and fat distribution), lean body mass and bone mineral content and density. New methods and longitudinal studies have expended our knowledge of these remarkable changes. Human differences in adiposity, fat free mass and bone mass reflect differences in endocrine status (particularly with respect to estrogens, androgens, growth hormone and IGF-1), genetic factors, ethnicity and the environment. During puberty, males gain greater amounts of fat free mass and skeletal mass, whereas females acquire significantly more fat mass. Both genders reach peak bone accretion during the pubertal years, though males develop a greater skeletal mass. Body proportions and fat distribution change during the pubertal years as well, with males assuming a more android body shape and females assuming a more gynecoid shape. Pubertal body composition may predict adult body composition and affects both pubertal timing and future health. Sexual dimorphism exists to a small degree at birth, but striking differences develop during the pubertal years. The development of this dimorphism in body composition is largely regulated by endocrine factors, with critical roles played by growth hormone and gonadal steroids. It is important for clinicians and researchers to know the normal changes in order to address pathologic findings in disease states.

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          Most cited references 33

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          Examination of US puberty-timing data from 1940 to 1994 for secular trends: panel findings.

          Whether children, especially girls, are entering and progressing through puberty earlier today than in the mid-1900s has been debated. Secular trend analysis, based on available data, is limited by data comparability among studies in different populations, in different periods of time, and using different methods. As a result, conclusions from data comparisons have not been consistent. An expert panel was asked to evaluate the weight of evidence for whether the data, collected from 1940 to 1994, are sufficient to suggest or establish a secular trend in the timing of puberty markers in US boys or girls. A majority of the panelists agreed that data are sufficient to suggest a trend toward an earlier breast development onset and menarche in girls but not for other female pubertal markers. A minority of panelists concluded that the current data on girls' puberty timing for any marker are insufficient. Almost all panelists concluded, on the basis of few studies and reliability issues of some male puberty markers, that current data for boys are insufficient to evaluate secular trends in male pubertal development. The panel agreed that altered puberty timing should be considered an adverse effect, although the magnitude of change considered adverse was not assessed. The panel recommended (1) additional analyses of existing puberty-timing data to examine secular trends and trends in the temporal sequence of pubertal events; (2) the development of biomarkers for pubertal timing and methods to discriminate fat versus breast tissue, and (3) establishment of cohorts to examine pubertal markers longitudinally within the same individuals.
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            Risk factors for hip fracture in European women: the MEDOS Study. Mediterranean Osteoporosis Study.

            The aims of this study were to determine common international risk factors for hip fracture in women aged 50 years or more. We studied women aged 50 years or more who sustained a hip fracture in 14 centers from Portugal, Spain, France, Italy, Greece, and Turkey over a 1-year period. Women aged 50 years or more selected from the neighborhood or population registers served as controls. Cases and controls were interviewed using a structured questionnaire on work, physical activity, exposure to sunlight, reproductive, history and gynecologic status, height, weight, mental score, and consumption of tobacco, alcohol, calcium, coffee, and tea. Significant risk factors identified by univariate analysis included low body mass index (BMI), short fertile period, low physical activity. lack of sunlight exposure, low milk consumption, no consumption of tea, and a poor mental score. No significant adverse effects of coffee or smoking were observed. Moderate intake of spirits was a protective factor in young adulthood, but otherwise no significant effect of alcohol intake was observed. For some risks, a threshold effect was observed. A low BMI and milk consumption were significant risks only in the lowest 50% and 10% of the population, respectively. A late menarche, poor mental score, low BMI and physical activity, low exposure to sunlight, and a low consumption of calcium and tea remained independent risk factors after multivariate analysis, accounting for 70% of hip fractures. Excluding mental score and age at menarche (not potentially reversible), the attributable risk was 56%. Thus, about half of the hip fractures could be explained on the basis of the potentially reversible risk factors sought. In contrast, the use of risk factors to "predict" hip fractures had moderate sensitivity and specificity. We conclude that variations in lifestyle factors are associated with significant differences in the risk of hip fracture, account for a large component of the total risk, and may be of some value in selecting individuals at high risk.
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              Weight status in young girls and the onset of puberty.

              We sought to examine the association between weight status in early childhood and onset of puberty. The study included 354 girls from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development. Girls were followed longitudinally with height and weight measurements at 36 and 54 months and grades 1, 4, 5, and 6 and with assessment of pubertal stage by physical examination and maternal report in grades 4 through 6. The main outcome was the presence of early puberty, indexed as follows: (a) breast development at or more than Tanner stage 2 by physical examination at grade 4; (b) breast development at or more than Tanner stage 3 by physical examination at grade 5; (c) maternal report of breast development at or more than Tanner stage 3 at grade 5; and (d) maternal report of menarche having already occurred (yes versus no) at grade 6. Multiple logistic regression models predicting early versus late puberty were constructed by using the covariate BMI z score at 36 months, rate of change of BMI and accelerated BMI between 36 months and grade 1, race, maternal education, and maternal age of menarche. BMI z score at 36 months, rate of change of BMI between 36 months and grade 1, an earlier age of maternal menarche, and nonwhite race were each consistently and positively associated with an earlier onset of puberty across the various measures of puberty. Higher BMI z score in girls as young as 36 months of age and higher rate of change of BMI between 36 months old and grade 1, a period well before the onset of puberty, are associated with earlier puberty, which suggests that increasing rates of obesity in the United States may result in an earlier average age of onset of puberty for US girls.
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                19115520

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