Abstract
Physical changes of sexual maturation and their clinical relevance are discussed in the first part, and the timetable of development in Swiss girls and boys as established from the Zurich longitudinal study is presented. The second part deals with changes in body size and shape and aspects of skeletal maturation. Prepubertal height is nearly identical in both sexes. During puberty important sex differences become evident and maturation is faster in girls by about 2 years. Puberty bigins at the same stage of skeletal maturation (sesamoid bone) in both sexes, and milestones (e. g. peak height velocity) are reached at the same degree of maturation. For bone age estimation, the Greulich and Pyle method is frequently used, but depending on the situation, that of Tanner et al. may be more useful. For height prediction, the methods of Bayley and Pinneau, Roche et al. and Tanner et al. are most widely used. None of them is always the most accurate one, but depending on the condition and relation between bone and chronologic age, the criteria for selection are discussed. Sex hormones modulate body proportions but have no influence on adult height. Adult height and velocity of maturation are independent multifactorial variables. The sex difference in adult height (12.5cm in Switzerland) is due to several components. Puberty is also characterized by changes in body composition. Lean body mass increases early in boys and girls. In girls, it peaks at menarche and then diminishes. The amount and distribution of water increases in boys and decreases in girls secondary to the greater accumulation of fat in girls. Hormonal changes during puberty are discussed in the last part. Basal gonadotropin levels increase, FSH more in girls than in boys, LH about equally in both sexes. More important is the advent of rhythmic, pulsatile gonadotropin secretion. The most obvious changes are the increasing secretion rates of sex steroids. To avoid extreme variation of normal values, estradiol and testoserone should be related to bone age and/or pubertal stages rather than to chronologic age. The role of DHEA in puberty is unclear. It increases before puberty at adrenarche. Also growth hormone, its binding protein, and IGF I and its binding protein 3 increase. Finally, synergistic metabolic effects between GH and sex hormones with examples using the stable isotope 15N are discussed.
