Continual change is the essence of life. The rapid changes in size that we call growth, and the rapid changes in form, function and behavior that we call development, are the core of pediatrics. A good working knowledge and the skill to evaluate growth and development are necessary in the diagnostic evaluation of any patient. Subtle changes—often the failure of some change or event to occur at an expected time—may constitute the earliest sign of disease. The early recognition of growth failure or maldevelopment may be the discovery that sets in motion the investigations necessary for effective intervention in the management of a patient's problem.

Assessment of Growth

The proper evaluation and use of anthropometric measures such as height, weight, and head circumference must be accorded equal status with other clinical data. The greatest difficulty lies in the definition of normality. This is generally done statistically. Unfortunately this often leads to the common error of assuming that the average or median value represents the optimum for a given patient. That this is erroneous is clear if one imagines 100 normal children of the same age but all of different weight. Only 1 child (the median, 50th percentile child), heavier than half the others but lighter than the other 50, would be considered normal, even though this violates the original premise that all the children are normal.

The necessary concept that there is a wide range of normal allows another kind of error, that of accepting as normal for an individual some value that falls within the normal range but is in fact abnormal for the given child. This is compounded by the fact that to the eye, and in figures on paper, such abnormality may not be apparent even to the most practiced eye of a skilled physician. For this reason, it is absolutely necessary to plot the parameters of growth on a suitable graphic chart. Plotting the data brings to light even slight departures from the expected path. Small changes such as the failure to gain 1 kilogram in 3 months are at once apparent. Serial data thus plotted constitute the best standard of normality for the individual.

It is well established that the individual grows in a "channel," probably genetically determined, and that such channel is specific for the individual. Departures from this channel, with rare exceptions, occur only in the event of noxious influence (e.g., disease, calorie excess or deficit, or even psychic disorder). When such departures occur, a return to the original channel will be observed if the cause is repaired. In the case of growth failure, for example, this return occurs by "catch-up" growth, which represents the fastest growth rate known. When dealing with a sick child, in the absence of earlier serial data, this "turning the corner" from catch-up growth into a channel that parallels a designated percentile guide is a good, and often the only, means of identifying the channel normal for that child until there has been an opportunity to accumulate sufficient serial data.

The charts in most common use have been based on measurements of populations of presumed normal children. One should have some familiarity with the base data. Is the chart based on "over 200 children living in Boston," or was it derived from a population of Iowa farm children? There is now a group of charts that set a more recent standard, derived from NIH studies covering a wider spectrum of the United States. The Wetzel grid, although never very popular and little used, has the unique property of having been developed on theoretic grounds instead of being a statistical description of a population. This grid plots "developmental level," a parameter related to physique, surface area, and basal metabolic rate, against age. It has been shown to be valid for any population or species. Another type of chart (Tanner) has been developed that depicts the rate of growth versus unit of time. This is particularly useful in studying the changing rates of growth that are characteristic of various periods of life and in relating the events of puberty and adolescence to physical growth. It will be referred to later. As it happens, if one adheres to the standard of normality consisting of following a channel (maintaining percentile rank), any of the charts alluded to can serve the purpose, although the percentile ranking may vary with the chart used. All these charts are designed to have increments of measure plotted against time and thus represent achieved status at any given age.

Normal Growth Rates

Humans grow at different rates at different times of life; there are rate differences between the sexes and various tissues have different rates of growth at the same time. Obvious examples are the fact that girls of 13 or 14 are often the same or even greater height than their male peers and then are surpassed in stature by males within a couple of years. The lymphoid structures of a child grow so rapidly that within 6 or 7 years they achieve status far exceeding 100% of adult size and are in fact receding during adolescence when the body as a whole (skeletal, muscle mass, and blood volume) is increasing in the rate of growth. Thus a second grader's tonsils may be very large and yet not be enlarged; a young child's spleen may become palpable during any infection, and mesenteric adenopathy is ever present in the differential diagnosis of appendicitis in children.

The human head grows so fast that it reaches near adult size in only 6 years. This rapid head growth necessitates birth for humans, unlike other mammalian species, at a time long before walking is possible. Were this not so, the head could not pass the pelvic outlet. Special charts are used to follow this phenomenon. Because the skull is so readily expansible, increasing intracranial pressure may manifest few other signs; papilledema, for example, may not occur if the sutures are not knit.

Human growth curves are characteristic of the species. After conception, there is a lag phase that soon becomes logarithmic. Term birth occurs during the logarithmic phase so that at birth the child is growing at the rate of 9 to 10 kg/yr. This growth rate declines almost asymptotically, and by the end of the first year growth is proceeding at a much slower pace of 2 to 2.5 kg/yr. This marked reduction of rate can be regarded as the physiologic marker of the end of infancy.

It is notable that major inflections of the growth curve are also associated with signal developmental events, for example, the accomplishment of locomotion and its psychodynamic companion, the first autonomy struggle. Nutritional requirements are high during periods of rapid growth and hence deficiency states are most likely in their wake. Characteristically clinical scurvy, rickets, and iron deficiency anemia arise during the latter half of the first year. Similarly, at the next inflection, the adolescent growth spurt, we find increased vulnerability to depletion of calcium and iron stores and another autonomy struggle, this time involving separation from home and both parents, whereas the first one, the "terrible twos," represented chiefly separation from mother. Awareness of these growth phases and their attendant psychodynamic implications enables the examiner to anticipate patient behavior and facilitates establishment of effective rapport as well as suggesting normal and pathologic phenomena to be searched for.

Stages of Development

It is useful to conceive of developmental periods, each characterized by certain tasks to be accomplished. The failure to accomplish these developmental tasks is evidence of disease, either past or present.

Conclusion

Continual change is the essence of life. The cessation of growth at the end of adolescence is not the end of development. Development of physical prowess, skill, and mental processes continues for many years. Even middle age does not interrupt development. Inevitably a process of involution begins. Like growth in earlier years, it affects different tissues and structures at different rates, slowed at first by the replacement of declining functions with newfound skills and bionic parts. Ultimately, however, change ceases—life ceases.

And so it is that no two patients with the same diagnosis have the same disease. Their problem formulations will be different, and their appropriate managements cannot be the same.

References

1. Knobloch H, Pasamanick B. Gesell and Amatruda's developmental diagnosis. New York: Harper & Row, 1974.
2. Lowrey GH. Growth and development of children. Chicago: Year Book Medical Publishers, 1978.
3. Tanner JM. Growth at adolescence. 2nd ed. Oxford: Blackwell, 1962.
4. Tanner JM, Whitehouse RH, Takaishi M. Standards from birth to maturity for height, weight, height velocity, and weight velocity: British children, 1965. Arch Dis Childh. 1966;41:613. [PMC free article: PMC2019692] [PubMed: 5927918]
5. Wetzel NC. In: Glasser O, ed. Medical physics. Chicago: Year Book Medical Publishers, 1944.