Physiology of normal growth

Human growth is influenced by environmental, genetic and hormonal factors. Epidemiological studies have shown that non-pathological factors such as nutrition, psychological influences, physical activity and climate play important roles on growth. The secretion and action of growth hormone can be disrupted by mutations in genes affecting the synthesis of growth hormone itself, its binding proteins and receptors or the production of pituitary transcription factors. Other hormones – e.g. thyroid hormone, adrenal androgens, sex steroids, glucocorticoids, ghrelin, leptin and insulin – also interact with the growth hormone-insulin-like growth factor-1 axis. Human linear growth starts from fertilisation and progresses through prenatal, infantile, early childhood and adolescent phases to be completed by fusion of the epiphyseal growth plates. After the rapid growth of foetal life, a marked deceleration follows in the first 3 years of postnatal life, which then leads to a slowly decelerating childhood component and finally a sigmoid-shaped pubertal phase. A thorough understanding of the normal pattern of human growth and the factors affecting this process is necessary for clinicians to evaluate patients referred with possible growth disorders and to identify those who require further medical input.