6. Growth Flashcards
How is normal growth controlled?
Controlled by complex interaction of
Factors
- Nutrition
- Environment
- Internal Signaling Systems – hormones and growth factors
What are the 4 stages of growth?
- Foetal
- Infant (rapid)
- Childhood
- Pubertal (rapid)
What are the requirements for Normal Childhood Growth?
- Absence of Chronic Disease
- Emotional Stability, Secure family environment
- Adequate Nutrition (most over nourished but obesity is not an indicator)
- Normal Hormone Actions
- Absence of defects impairing cellular/bone growth
Why is growth monitoring important?
Monitoring growth extremely important as it is often how chronic illness is detected.
Health Surveillance, Should be carried out at all hospital visits. Done a lot in paediatrics, because of drug/dosing requirements.
How does chronic illness impact on childhood growth?
- Potent cause of growth failure
- Primary effect of disease on dividing cells
- Secondary effects on nutrition
- This is why growth monitoring is such an important part of child health surveillance
Dramatic growth failure caused by emotional deprivation? MOA? Tx?
Emotional Dwarfism.
No problem with growth hormone levels but it is not able to perform its function. In orphanges, there can be practical care, but little emotional care and this is bad.
Growth normalises when child removed from initial environment
What is the contribution of growth to Total Energy Expenditure?
Energy requirements for normal growth are modest
Growth makes the smallest contribution to Total Energy Expenditure ( 5-10%)
At what stage is the rate of foetal growth the highest? Rate? Pattern?
Growth velocity maximal in 2nd timester
Equivalent to 62cm /year
Linear Pattern of Growth (different to weight gain).
Discuss the pattern of weight gain in foetal growth?
40 Weeks
4-12wks = 0.1kg/yr 12-14wks = 2.7kg/yr 24-40 = 8.7kg/yr
Note: Childhood = 2-2.5kg/yr
What factors determine the rate of foetal growth?
Foetal growth constrained by..
- Maternal factors
- Placental function
It is coordinated by growth factors
So the size of the baby at birth is dependent on the intrauterine environment and not the genetics.
Discuss the role of the placenta in foetal growth?
Plays a rate limiting role
You can have a healthy mum, but an unhealthy placenta and vis versa.
Over/under eating during pregnancy does not have much of an effect.
What are the demands of Pregnancy on Total Energy Expenditure?
Overeating/undereating during pregenancy not much effect Calorific demands of pregnancy about 1/2 banana a day. So you are NOT eating for two
How does foetal growth affect health in later life?
- Related to health in later life
- Hypertension
- Cardiovascular Disease
- Cerebrovascular Disease
- Insulin Resistance
- NIDDM
What growth pattern is seen in infants?
An infant loses 5-10% of its birth weight but should regain it by 2 weeks
An infant doubles its birth weight by 4-6 months
Year 1 infants grow rapidly but at a sharply declining rate
Similar pattern has been observed for their weight.
What is the principle regulator of growth in the infant stage?
NUTRITION is the principal regulator of
growth over this period.
GH/IGF axis have a certain limited role
If nutrition is not good at this stage it will be difficult to catch up
What is the main determinant of size at the end of all growth?
The actual size of you is genetic, almost entirely, aside from any significant pathological interuption of growth
What does early obesity in infancy suggest?
More likely to lead to tall stature developing later in childhood
What relationship between birth weight+length and mid parental size?
At birth poor correlation between length, weight and mid parental size
When does the correlation between length and mid parental height emerge? How?
By 2 years good correlation between length and mid parental height.
Achieved in the 1st 2 years by:
- Catch up (accelerated growth) 6-18months
Or - Catch Down (Decelerated growth) 3-6 months and 9-10 months.
*From small/large birth weight which is intrauterine determined.
What is the growth velocity by around 4 years?
7cm/yr
What happens to the growth velocity after 4 years?
Thereafter declines steadily until adolescence
The prepubertal nadir (lowest VG) = 5cm
However:
• Definite mid-childhood growth spurt
• Seasonal variation in growth
What determines childhood growth?
GH and Thyroid hormone are the major determinants of growth in childhood.
Normal growth depends on inherent genetic mechanisms and external influences.
Therefore childhood is when a majordysfunction in the GH axis may be recognised.