Prof. Dr. Michael Hermanussen

Acceleration

Acceleration (lat. accelero - I accelerate) describes the positive change in developmental tempo in children.

Usually acceleration coincides with a positive secular change towards a rise in final stature. The age of the first menstrual bleeding (menarche) has decreased by almost 4 years since the mid-19th century, and currently occurs at an age of about 13 years in central Europe.

AnthropometryAnthropometron

Anthropometry (greek anthropos, human being) describes the theory of measuring the human being. The earliest device ever published for measuring body stature was described in 1654 by Johann Sigismund Elsholtz (Figure). It illustrates the measuring device with a movable board (regula) above the head, and the basis to stand on.

A period of increased growth velocity that compensates for a period of reduced growth velocity.

Catch up growth usually occurs after illness or starvation and enables a child to regain his/her original growth channel that was lost during the period of growth failure.

Constitutional acceleration of growth and development

Many healthy children grow and develop at faster tempo the others. They tend to be taller during childhood and adolescence and enter puberty ealier than their age mates. yet, they usually do not stay tall. The constitutional acceleration of growth and development is a normal variant of growth and appears to be partially hereditary.

Prior to assuming that a certain child is constitutionally accelerated, various illnesses must be excluded. Endocrine tumors may influence the developmental tempo, particularly girls may enter puberty early. In these cases, the acceleration of bone maturation may lead to an early closure of the epiphyseal growth plates – and often to a decrease in final height.

Constitutional delay of growth and development (CDGD)

Many healthy children tend to develop at slower pace than others. They are often short during childhood and adolescence and enter puberty late.

Girls tend to have menarche late. However, children with constitutional delay of growth and development tend to catch up with their age mates, i.e., they do not stay short. CDGD is a normal variant of growth and appears to be partially hereditary.

Developmental tempo

The tempo, or the velocity at which a child matures, differs between the children. Some adolescents though aged 12 years, still look like 10 years old ones, they are as tall as their 10 year old mates, and still wait for their pubertal development; other 12 year old ones almost look adult, and among other signs are also sexually more mature than their age mates.

Aspect and biological maturity often differ from psychological and school development, but biological maturity usually correlates with growth and bone maturation. Children who mature at slow pace, usually also show a delayed bone age (or skeletal age), they are called constitutionally delayed. Children who mature at fast pace in whom bone age is more advanced than chronological age are called constitutionally advanced.

Epiphyseal growth plate

The Epiphyseal growth plate consists of a small cartilaginous disc between diaphysis (the long part of a long bone) and epiphysis (the distal part of a long bone). Long bones usually have two Epiphyseal growth plates. These plates are well organized, cartilage celles are not only closely packed, but show a distinct "column-like" appearance. This characteristic feature is necessary for the direction of growth. Epihysenfuge

The Figure shows a thigh bone (left), and a small enlarged section (center). There is an obvious column-like structrue of the cells (schematic view at the right side).

Epiphyseal growth plates become smaller during childhood and adolescence and finally ossify in a strictly regulated sequence during puberty or a little later. When the plates have fused – usually after puberty – and when they are completely ossified longitudinal bone growth stops. Not all growth plates mature at the same speed. Therefore - particularly during puberty - body proportions change.

Final height, maximum height

Maximum body height is usually reached at the beginning of the third decennium. Also young adults still grow, though only in the trunk. Growth of the legs already stops at an age of 14-16 years in boys, and even earlier in girls. Thereafter, growth is limited to trunk growth, and the "strange" long-legged mid-pubertal proportions normalize. After the mid-thirties most people start to shrink, though at very slow rates of about one millimeter per year. Intervertebral discs shrink, and with increasing age, also the vertebral bones shrink due to osteoporosis (loss of bone material) and little fractures. And the arches of the feet flatten.

Frankfurt plainFrankfurter Ebene

Measuring stature is not that simple. Usually, a person is asked to stand upright against a vertical wall looking straight ahead. For reasons of comparability, the head should be held in a defined position. It has become international routine to position the lower orbital ring and the auditory meatus along a horizontal line (the so called Frankfurt plain, Frankfurter Ebene).

GigantGigantism

We talk about true gigantism when body height surpasses 7 1/2 feet, i.e. 229 cm, other authors talk about 8 feet, i.e. 244 cm.

This size is very rare, and can only be achieved during long periods of excessively elevated growth hormone production during childhood. Elevated growth hormone production in adults results in acromegalie. Acromegalie is much more common and may be regarded the adult form of gigantism. After most epiphyseal growth plates have fused, longitudinal growth is terminated. Only the tips of the fingers, the nose, the acra may go on growing. Acromegalic patients have a typical coarse face.

growth tracks

SDS patternsChildren of the same age are not equal in stature. Body height varies around mean height and can be expressed as SDS (standard deviation score). This means, body height can be expressed relative to mean height. 95 percent of all height measures vary between minus two and plus two height-SDS. The remaining children are taller or shorter, i.e. their body height differs by more than 2 SDS from mean height. Children grow and become taller in terms of centimetres, but they can remain on the same height-SDS for many years. Some children grow faster than others, they change height-SDS. Growth tracks are patterns of height-SDS. Children who grow at average velocity persist on their former height SDS, they grow horizontally and have horizontal growth tracks. Children who grow slower than their peers, show declining growth tracks. Children who grow faster than their peers, show increasing growth tracks. The idea of growth tracks replaces the traditional ideas of growth as a strictly "canalized" process. The graph illustrates three height SDS patterns of girls. The upper girl grows at average tempo, the second girl - late maturing - at retarded and the third girl - early maturing - at accelerated tempo. Mid-puberty (the moment of peak height velocity) is indicated by the vertical line. Average tempo of growth is characterized by horizontal patterns, retarded tempo by a downward SDS peak (usually before the age at peak height velocity), accelerated tempo by an upward peak (usually after the age at peak height velocity).

Harris linesHarris Linien

Harris Lines are dense traversal structures that can sometimes be viewed in X-rays of long bones parallel to the epiphyseal growth plates.

Harris Lines are expressions of a previous disturbance in longitudinal bone growth. After periods of growth arrest, e.g. due to illness or malnutrition the subsequent catch-up growth leads to slightly modified bone development that can be detected for many years in later X-rays.

Many Bronze age people suffered from early spring starvation in Northern Europe. Also their children starved, and probably also suffered from periodical growth arrests. The picture illustrates X-rays of bone fragments of people who died as adolescents and were burned and buried in urnes. Still, Harris Lines can be observed, occuring at annual rings similar to trees. We believe that these lines occured during and after early spring starvation.

Height and social status

Since a long time the interaction between body height and social status is known. Almost all US American presidents were taller than the average population. Aristocrates and kings used to be 10 to 15 cm taller than farmers, up to the 18th century.

Normal values, reference values

Normal often means: frequent. Normal values for height, weight etc. usually mean that these values are frequently observed within a population. Normal values do not provide information on health or illness; in other words, one can never say that somebody who is much taller, shorter, heavier or lighter than average, is not healthy. Normal values often serve as reference values, i.e., body height, weight etc. of a certain child is compared with its respective reference value.

Values for height, weight etc. scatter around the mean. Variation can statistically be expressed via the standard deviation. We can relate height, weight etc. of a child to its reference value. In this case we may use SDS-values (z-values) or percentiles.

Percentiles, centiles

Percentiles (or centiles) express height, weight etc. of a child in percent. It means that height and weight are related to height and weight of his/her age mates. Height at the 50th percentile means that 50% of the age and sex mates are shorter than that child; height at the 3rd percentile means that exactly 3% of the other children of that age and the same sex are shorter .

Body height below the 3rd percentile is usually referred to as short stature, height above the 97th percentile as tall stature. Percentiles are given for height, weight, BMI and many other biological parameters.

Obesity

Obesity or adiposity is defined as an illness characterized by pathological fat tissue increments. A comparably good indicator of obesity is the BMI. Apart from few exceptions, obesity is diet-related.

Today, average weight of the population, and the number of obese persons increase in all Western societies. In Germany, average conscript weight continuously increases by some 400 gram per annual cohort.

The increasing prevalence of obesity is already visible during childhood. The illness usually starts at early age (5-6 years). Obesity causes many secundary metabolic diseases, diabetes, illnesses of the cardiovascular system, and orthopedic problems.Venus von Willendorf

Obese persons have always been observed. One of the first descriptions is the well-known Venus from Willendorf.

Standard deviation score (SDS) or z-value

Body height, weight and many other parameters can be described by absolute terms, i.e. in centimetres, kg and other dimensions. But they can also be expressed in relative terms. Reference values for height of a population can be defined by mean and standard deviation. If we want to express height of a certain child relative to his/her age and sex mates, we use z-values or standard deviation scores (SDS). SDS are calculated:

SDS = (measured value - population mean)/Standard deviation

All values between -2 SDS and +2 SDS are by definition normal.

Target height

Target height is expected height of a child or adolescent based on parental height. according to Tanner (1986) target height is calculated:

male target height = (father's height + mother's height)/2 plus 6 cm

female target height =  (father's height + mother's height)/2 minus 6 cm

According to Hermanussen and Cole (2003), target height can be given in height SDS and is calculated: target height SDS is mean height SDS of the father plus mean height SDS of the mother multiplied by 0,72.