Normal growth

Growth in children can be divided into three stages (Fig 43.1). Rapid growth occurs during the first 2 years of life; the rate is influenced by conditions in utero, as well as the adequacy of nutrition in the postnatal period. The next stage is relatively steady growth for around 9 years and is controlled mainly by growth hormone (GH). If the pituitary does not produce sufficient growth hormone, the yearly growth rate during this period may be halved and the child will be of short stature. The growth spurt at puberty is caused by the effect of the sex hormones in addition to continuing GH secretion. The regulation of GH secretion is outlined in Figure 43.2.

GH is only one of many hormones involved in growth. Insulin-like growth factors, thyroxine, cortisol, the sex steroids and insulin are also involved.

Growth hormone insufficiency

Any child whose height for age falls below the 3rd centile on a standard chart, or who exhibits a slow growth rate, requires further investigation. If GH deficiency is diagnosed, and treatment is required, then the earlier it is given the better the chance that the child will eventually reach normal size.

Growth hormone insufficiency is a rare cause of impaired physical growth. It is important to differentiate between children whose slow growth or growth failure is due to illness or disease and those whose short stature is a normal variant of the population. Causes of short stature are:

Standard graphs relating age and height are available for the normal population. Accurate measurements of height should be made to establish whether a child is small for chronological age. These measurements are repeated after 6 and 12 months to assess the growth rate. The height of the parents should also be assessed. The bone age is the best predictor of final height in a child with short stature; this is determined by radiological examination of hand and wrist. In most growth disorders bone age is delayed and by itself is of little diagnostic value, but taken together with height and chronological age, a prediction of final height may be obtained.