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Normal Pubertal Development SOMATIC CHANGES Puberty is characterized by an increase in growth rate and the appearance of striking somatic sex differences. The onset of these changes actually antedates the appearance of secondary sex characteristics by a few years. Thus, sexual maturation is a considerably longer process than the period of visible changes induced by marked incremental increases in gonadal hormones. Unlike boys, girls augment their body fat noticeably at 7 years of age; by 16 years of age girls have twice as much fat as boys. Total body water reflects lean body mass, which is made up primarily of muscle and skeletal tissues. At 9 years of age, total body water increases significantly in boys and signals the onset of more rapid growth in lean body mass. Muscle mass in boys doubles between the ages of 10 and 17 years, and skeletal mass doubles between ages 12 and 16 years. During adolescence boys exceed girls in all body measurements except hip width and body fat. The changes in body constituents during puberty are reflected more impressively by increases in height and weight. The initiation of the adolescent growth spurt precedes the onset of secondary sex characteristics by approximately 1 year in boys and girls.
The Biological Aspects of Puberty
Howard E. Kulin MD1
Jørn Müller MD2
1 Professor of Pediatrics and Chief, Division of Pediatric Endocrinology, Pennsylvania State University College of Medicine, Hershey, PA.
2 Consultant in Pediatrics, Department of Growth and Reproduction, National University Hospital, Copenhagen, Denmark
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