In mammals, the major factors involved in the regulation of body growth are known: insulin-like growth factors (IGF) are key regulators of somatic growth. Growth hormone (GH), secreted by the pituitary gland, directly regulates circulating levels of IGF-I, which is the major coordinator of spatio-temporal growth of the organism. In humans, growth is even more complex, involving a number of specific characteristics not found in other species. These include rapid intrauterine growth, deceleration just after birth, a mid-childhood growth spurt, a second deceleration before puberty, an...