The first 2 years of life represent a transition period when growth changes from predominantly growth hormone (GH) independent to GH dependent. In the fetus, growth is influenced by genetic and environmental factors in addition to nutrition and growth factors including insulin. In infancy, nutrition remains an important determinant of growth. GH levels are high in mid-gestation and at birth, then fall sharply for the first few weeks and more slowly over the next few months reaching pre-pubertal levels by around the age of 6 months. GH deficiency (GHD) may present at birth with hypoglycaemia, micropenis or prolonged conjugated hyperbilirubinaemia. Although length at birth is usually within the normal centile ranges, post-natal growth failure can begin early and be profound.