Height velocity curves in normal and abnormal situations: Relationships between diseases - achondroplasia, cystic fibrosis, growth hormone deficiency and hypothyroidism

This chapter reviews our understanding of normal growth, with an emphasis on height velocity, in average stature children. It will also include discussion of landmarks of pubertal development as it relates to growth and growth velocity. Additional considerations to optimize growth assessment include appreciation of the differences between cross-sectional and longitudinal measurements, and the symmetry/congruence (or lack thereof) of growth parameters. Two variants of normal growth, familial short stature and constitutional growth delay, are also compared. Our understanding of growth and height velocity in average stature children is then compared to that of children with achondroplasia, a short stature skeletal dysplasia that dramatically limits linear growth through effects on the growth plates of bone that are essential for linear growth regulation. It will compare achondroplasia, whose growth defect cannot be overcome by current medical measures, to other growth-limiting conditions with graded responses to nutritional or medical interventions, including cystic fibrosis and growth hormone and thyroid hormone deficiencies. These conditions demonstrate the importance of obtaining height velocity measures and that nutritional insufficiency must be distinguished from congenital, constitutional, familial, and endocrine disorders to properly understand and address growth defects.