Normal growth and its endocrine control

Growth begins at conception and reaches a peak in terms of height velocity during the second trimester, when the crown-heel rate attains a speed of 2 cm/week, the fastest the individual will ever grow. After that peak has been achieved, the velocity falls to around 5 mm/week at term. The increment in the first year of postnatal life is about 25 cm so that fetal and early postnatal growth account for nearly half of all the growth in adult length.

This broad brush summary conceals a wealth of ignorance of detail about growth at a critical time. Fast dividing cells are especially susceptible to adverse environmental circumstances and yet we know next to nothing about the complexity of factors which must govern the growth process at this critical time. This is clearly demonstrated by our inability to influence, or rather to correct, abnormal growth in utero and by our poor showing in attaining normal growth rates of premature infants in the newborn nursery.

Postnatal growth

The human growth curve has never been better exemplified than by that most famous of curves, the growth in length of the son of Count Philibert Gueneau de Montbeillard between 1759 and 1777 (Fig. 2.1). The upper panel of this Figure, the distance chart, shows the length as measured at 6-monthly intervals; the lower panel, the velocity chart, shows the annual increments plotted against the chronological age at the mid-points of each whole year.