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      A Biologically-Oriented Mathematical Model (ICP) for Human Growth

      Acta Paediatrica
      Wiley-Blackwell

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          The adolescent growth spurt of boys and girls of the Harpenden growth study.

          Logistic curves have been fitted to the growth during puberty of the 55 boys and 35 girls of the Harpenden Growth Study who were measured every three months during puberty and thereafter until growth ceased. Very good fits were obtained for stature, sitting height, subischial leg length, biacromial and bi-iliac diameters from approximately six months after the beginning of the adolescent spurt. This beginning, called "take-off", was determined graphically as the point of minimum velocity. The total height gained from take-off point to cessation of growth averaged 28 cm in boys and 25 cm in girls with standard deviations of about 4 cm. The adult sex difference in height was due much more to the later take-off in boys than to a greater male adolescent spurt. A sex difference in the spurt occurred in sitting height but not in leg length. Mean-constant curves for the four measurements are presented. In each measurement size at take-off and total adolescent gain were nearly independent, the average correlation coefficient being --0-2. The correlations between adolescent gains in different measurements averaged only 0-47, and between peak velocities of different measurements only 0-27. This implies considerable shape change at adolescence. In contrast the average correlation between ages at which the peak velocities were reached was 0-87. Ages at take-off, at peak velocity, and at menarche were independent of mature size, though correlated with percentage of adult size reached at the ages in question, a measure of somatic maturity. Relationships with the development of breasts, pubic hair and genitalia were examined; ages at take-off and at peak velocity correlated to the extent of 0-6 to 0-8 with ages of B2 and PH2 but both these parameters and also peak velocities were uncorrelated with the rapidity with which sex characters developed.
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            On the modelling of human growth.

            J Karlberg (1987)
            A new approach to modelling human linear growth from birth to maturity is presented. The model splits growth into three additive and partly superimposed components, appropriately named infancy, childhood and puberty; we refer to it as the ICP-model for obvious reasons. A key feature of this model, compared with others, is that the components correspond with known features of the endocrinological regulation of growth and can be considered in isolation from one another.
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              Analysis of the adolescent growth spurt using smoothing spline functions.

              Height growth velocity curves between 4.5 and 17.75 years were estimated, using smoothing spline functions, for 112 boys and 110 girls from the Zurich Longitudinal Study (1955--1976). Parameters characterizing the growth process, such as peak height velocity and age at peak height velocity, were calculated directly from the estimated curves. The variability of parameters describing the adolescent growth spurt is large, both between and within sexes. Peak height, defined as increase of height velocity during the growth spurt, and age at peak height velocity both characterize the sex difference in growth in a highly significant manner. Peak height of at least 4 cm/year is found in 70% of the boys, but in only 11% of the girls. The age at peak height velocity averages 12.2 years in girls and 13.9 years in boys and has a wide range of 5.7 years and 3.8 years respectively. The sex difference in adult height of 12.6 cm is composed of the following 4 factors: +1.6 cm caused by more prepubertal growth in boys, +6.4 cm by the boys' delay in spurt, +6.0 cm by the more extensive spurt in boys and -1.4 cm by more post-spurt growth in girls. Correlations between parameters indicate that the adult height depends neither on the duration of growth, nor on the duration and height of the peak. Minimal pre-spurt height velocity and peak height velocity, but not peak height, are age- and height-dependent. Partial correlations given adult height reveal two compensating mechanisms between growth in the prepubertal and in the pubertal period. Small prepubertal height and low height velocity with respect to adult height are followed by a late adolescent spurt and vice versa. Small height at the onset of the spurt with respect to adult height is followed by a longer lasting, but not higher spurt and vice versa.
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                Author and article information

                Journal
                Acta Paediatrica
                Acta Paediatrica
                Wiley-Blackwell
                0803-5253
                1651-2227
                February 1989
                February 1989
                : 78
                : s350
                : 70-94
                Article
                10.1111/j.1651-2227.1989.tb11199.x
                2801108
                ff75085e-7339-4487-bbf4-b0ae3f7ddc22
                © 1989

                http://doi.wiley.com/10.1002/tdm_license_1.1

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