Download Human Life Cycle 4 – Physical Development in Childhood

Human Life Cycle 4 - Physical Development in Childhood
Anil Chopra
1.
2.
3.
4.
5.
Physiology of growth
Normal growth patterns
Abnormal growth
Obesity
Clinical cases and examples
Physiology of Growth
GHRH – growth hormone releasing hormone is secreted in the hypothalamus. It
travels to the anterior pituitary where it stimulates somatotrophs to secrete
somatotrophin (Growth hormone) and suppress the secretion of somatostatin.
Growth hormone is released in bursts, not a steady flow, most GH is made overnight.
The growth hormone travels in the blood via the binding GH binding protein. Growth
hormone results in the production of IGF 1 – insulin like growth factor 1 – an
anabolic agent which binds to IGF-1 receptors and stimulates skeletal muscle growth.
It is made in bone plates and in the liver.
Velocity = cm grown per year
Height = total growth up to now
Typical growth velocity curves:
Typical cumulative height growth curve:
Antenatal Growth: this is the fastest period of growth and is influenced by the
placneta and maternal nutrition.
Infancy: nutrition is an important factor and poor food intake or serious illness can
affect growth. Normal infants frequently cross centiles. GH is not an important factor
until late infancy.
Childhood: most children remain in their centile (which is generally determined by
genetic factors, previous events and chance) and grow at a similar rate. The important
factor is GH.
Puberty: rising sex steroid levels stimulate GH secretion causing a pubertal growth
spurt at the end of which the epiphyses fuse and growth stops. This results in skeletal
maturation. The timing of puberty does not affect adult height.
NB: boys have growth spurt later than girls
Cessation of Growth: the last growth is the spine and the last epiphyses to fuse are
the pelvis.
Parental height: an important factor in the child height (when plotting mother on
man’s chart, add 14cm, when plotting father on female chart, deduct 14cm)
Child has to grow at 50th centile velocity to maintain growth.
Causes of Short Stature
Short stature can be defined as one who is below the level of the lowest centile in
growth curve.
 Low birth weight
 Medical conditions
 Endocrine problems
o GH Deficiency – can be isolated or occur with other pituitary
problems. A stimulation test is done to diagnose the deficiency.
Treatment is recombinant DNA.
 Skeletal dysplasia and syndromes
o Turner’s syndrome – caused by 45XO karyotype and results in short
stature despite normal levels of growth hormone. Girls have ovarian
failure and hence inability to progress into puberty. Features include
webbed neck, wide carrying angle of arms, hypoplastic nails.
Psychological Aspects
Many families feel their children will be happier and more successful if they are
taller, however there is little solid evidence for tall people being happier or richer
once we take out other factors. People referred to hospital for short stature are a
selected group.
Height is normally distributed in the population:
0.13%
-3SD
2.28%
-2SD
15.87%
-1SD
50%
MEAN
84.13%
+1SD
97.72%
99.87%
+2SD +3SD
Obesity
Obesity is defined as having a BMI of over 30.
BMI is calculated as:
BMI = weight in kg/(height in metres)2
Adults
• BMI over 25 kg/m2 = overweight
• BMI over 30 kg/m2 =obese
Children
• BMI over 85th centile = overweight
• BMI over 95th centile = obese
BMI
40
35
kg/m2
30
25
20
15
10
boys
5
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Genetics of Hunger and Obesity
Hunger is controlled by a number of hormones:
Leptin: a hormone secreted by fat (adipose tissue) with receptors in the hypothalamus
and thus increased fat increases leptin secretion. There are some obese humans have
been identified with both leptin deficiency and leptin receptor mutations.
Obesity levels are increasing in many developed countries. This is due to the decrease
in physical activity and an increase in snack foods and high calorie foods in the diet.
This can be attributed to TV, internet, soft drinks, fast food, parental obesity and
education and social factors.
There are a number of associated risks with obesity:
• Acanthosis nigricans - marker of insulin resistance.
• Impaired glucose tolerance/type 2 diabetes
• Orthopaedic problems
• Polycystic ovarian disease
• Cardiovascular risk
Management of Obesity includes:
• Information and education
• Making healthy choices more available
• Public attitudes
• School initiatives
• Changes in food manufacture and advertising
Growth Charts
The accurate measurement of children forms the basis of growth assessment and
clinical decisions are based on theses assessments.
 >2 years
 standing height – stadiometer
 Younger children
 Supine length
 Sitting height
 compare body proportions
Estimations of growth
 BOYS – add 14 cm to mother
 GIRLS- subtract 14 cm from father
 Mid parental centile is midpoint
 target range is +/- 8.5 cm from mid centile