Growth is a dynamic process influenced by many intrinsic and extrinsic factors that interplay to determine not only ultimate attained height but also the tempo and timing of height increase. Research continues to unravel hormonal and genetic complexities that account for variations in "normal" growth, and etiologies for disordered growth. Careful tracking of childhood growth is a sensitive indicator of health and well-being, and therefore an essential component of sound pediatric care. Detection of unexplained acceleration or deceleration in growth rate or tracking along a disparate percentile for family should prompt investigation. Endocrine disorders comprise an important, but only partial differential diagnosis of abnormal growth. This chapter discusses essential components of normal growth, the detection and evaluation of worrisome growth, and diagnosis and treatment of its multiple etiologies. The ultimate goal is to provide for those caring for children a conceptual framework for the assessment of and diagnostic approach to the child with abnormal growth.
The rate of linear growth and the physiologic components regulating it vary with age. Conceptually, it is helpful to define growth as occurring in four discrete but congruent phases—prenatal, infancy, childhood, and adolescence (Figure 2-1). The range of growth velocities associated with these phases is depicted in Figure 2-2. Early detection of deviation from normal growth velocity is the key to prompt evaluation and diagnosis of a child with a growth abnormality.
Phases of childhood growth. (Redrawn from Karlberg J.On the construction of the infancy-childhood-puberty growth standard. Acta Paediatr Scand Supl. 1989;356:26.)
Ranges of linear growth velocities in males and females. (Modified from charts prepared by Tanner and Whitehouse, 1976, and reproduced with permission of Tanner JM and Castlemead Publications, Ward's Publishing Services, Herts, UK.)
Intrauterine growth occurs at a rate of approximately 1.2 to 1.5 cm per week, peaking at midgestation (18 weeks) at 2.5 cm per week and slowing to 0.5 cm just before birth. There are both intrinsic and extrinsic factors contributing to prenatal growth and ultimate birth weight and length. Future growth patterns and genetic height tendencies, however, are not necessarily reflected at this stage. Hormonal control is largely caused by insulin and insulin-like growth factors 1 (IGF-1) and 2 (IGF-2). Maternal and uterine factors affecting fetal nutrition, insulin availability, and insulin sensitivity also have profound effects on intrauterine growth. By comparison, growth hormone (GH) and thyroid hormone have only modest effects on in utero somatic growth.
After birth the rate of growth is simultaneously the most rapid and rapidly slowing of a child's growth experience, peaking at approximately 25 cm per year then declining approximately 15 cm per year during the first 2 years of ...