Lecture 15; Post Natal Growth 1 Flashcards
What determines fetal growth?
- Nutrition
- Hormones mediate the effects of nutrtion
Describe how nutrition effects fetal growth;
– Greater substrate supply: larger baby
– Restricted substrate supply: smaller baby
What hormones mediate the effects of nutrition in fetal growth?
– IGF-I & -II
– Insulin
– Paracrine factors: PDGF, EGF, FGF
– Less impt: Placental lactogen, thyroxine
What does Insulin Growth Like factor Two (IGF-2) deficiency cause?
IGF-2 Deficiency = small baby
IGF-2 imprinting = Organomeagly
Describe growth factor hormone function in the fetus;
There are high levels of growth factor hormone but does not promote linear growth before birth (No receptors in the liver)
(Unknown function)
What does mild hyperthyroidism prior to birth in the fetus cause?
Stunted growth
What are the effects of paracrine fators in the fetus?
Bone and tissue growth
Describe the relationship between nutrition and paracrine factors and the placenta?
Cant seperate factors (otherwise no growth)
Placenta
Increased supply of glucose + amino acids
= Increased fetal glucose + amino acids
Leads to = Increased Insulin (fetal pancreas) + IGF-1 (liver)
= Bigger (longer/fatter) baby
What factors do we need for growth after birth?
• Growth potential:
– Normal CHROMOSOMES, Parental Height
• Permissive factors:
– Adequate NUTRITION
– Caring ENVIRONMENT
– Good HEALTH
• Appropriate functioning HORMONES
What are the important growth hormones in infancy and childhood?
- GH
- IGF-1
- T3,T4
What are the paracrine factors and less important factors in childhood growth?
• Paracrine growth factors: PDGF, EGF, FGF •
Less important: Insulin
Describe the circulating levels of GH prior to birth and post;
30mg/L in fetus
1mg/L in baby
Describe the genetic determinants of growth;
Polygenic genetic compliment - determines growth
- Normal chromosome expression
- Normal health (illness effects growth)
Write some notes on how important hormones are together?
GH very important
- Direct and indirect effects of all hormones as they act together i.e low GH = low T3,T4
Limb growth requires paracrine factors
What is growth due to?
• Postnatal growth is due to both hypertrophy and hyperplasia. Genetic, hormonal and environmental factors replace maternal and placental influences of pregnancy.
Describe who the growth of limbs and CNS differs to body;
• a. Differential growth – legs get proportionally longer cf head
• b. Organ tissue growth – mostly parallels skeletal growth
– Brain / eyes well developed at birth – Reproductive tissues grow at puberty
What are the three phases of growth;
1) Infancy
2) Childhood
3) Puberty
Describe the rate of growth at infancy for both boys and girls;
rapid but decelerating i.e 24cm/yr
Describe the growth rates of boys and girls in childhood;
growth rate steadily decreases until just before puberty and continues to fall if puberty is delayed
- but parrallel in boys and girls until puberty
Describe the growth rate of boys and girls at puberty;
“growth spurt” (rapid but transient rise in growth rate) (falls after 2 years?)
- Girls inc @ ~10
- Boys inc @ ~13
- Occurs later and to a larger extent in guys
- Have a look at the graph for reproducibility
Why is there are difference in growth between boys and girls?
Height difference between boys and girls is because extra 2 years growth (prior to puberty) and faster rate of growth during puberty prior to epiphyseal closure
How much does genetics influence birth size?
Minor Influence
20% mum
2% dad
Describe the influence of genetics at puberty and postnatally;
- Major contribution to postnatal growth, likely polygenic
- Puberty is significantly genetically determined but social/nutritional environment are the main influence of age of menarche
Describe the differences in growth between males and females;
• Sex differences:
– Male fetuses have a slightly higher birth weight – Boy are slightly taller in childhood
At what point does insufficient nutrition stop growth?
• Nutrition
– protein-calorie intake < 82% to 91% of the recommended level will arrest growth.
– Adaptive response to poor environment!
Do children with IUGR catch up?
~80% show catch up growth
How does nutrition affect endocrine regulation of growth?
• Interacts with the endocrine regulation of growth
– Chronic disease: malabsorption, increased energy demand, inflammation decrease GH secretion
Basically as said earlier nutrition and endocrine functions are linked
Does over nutrition make you taller?
It makes you a taller teenager but ultimately it does not alter your genetically predetermined optimal growth
- Regression to the mean
Why does overnutrition only make you a taller teenager?
• Growth is advanced
– Enter puberty earlier
– Finish growing sooner
In terms of percentiles for weight and height vs age, what does undernutrition lead to?
Weights falls more than height
i.e on the percentile curves undernutrition will result in the weight falling off the percentile curves for age,
but the height wall fall to the bottom percentile trend curve for age.
What is the cause of undernutrition?
- inadequate nutrient intake (e.g. psychosocial feeding or eating disorders, poor appetite due to chronic disease)
- excessive nutrient loss (chronic vomiting, malabsorption)
- metabolic wastage (e.g., poorly controlled diabetes mellitus)
- deficiency of trace metals: zinc and copper
What does a normal person have on the percentiles for weight and height vs age?
They are in similar percentile groups for both categories i.e someone who is in the 90th percentile for height will be in the 90th for weight
What is the effects of undernutrition on final height?
• Initially growth is delayed
– i.e. can catchup if nutrition is restored (as this delay is a adaptive response)
• Final height will be reduced if sustained undernutrition
How can patients heights vs age be compared?
• SDS (= Z-score)
– (Height-mean for age) / population SD
(above or below the mean)
• Allows you to compare heights from children at different ages.
How can final height / growth age be predicted?
Bone ageing;
- Imprecise picture matching.
- 1 yr intervals.
- Tables for final Ht prediction.
- PAH very useful to distinguish FSS and CDGD for Dx and reassurance
Describe an equation for height prediction of a child;
Adjusted mid parental height = target height
i.e
- Boys: MPH = (F+M+13 cm)/2
- Girls: MPH = (F+M-13 cm)/2 • 95% MPH Range: 8cm)
What is the average difference in height between males and females in a population?
13cm
What is short stature?
Short Stature: height < the 3rd %ile (or < -2S.D. =2.3%)
What is severe short stature?
Severe short stature: height < -3 S.D. (below the mean)
What is failure to thrive?
Failure to thrive: failure to gain adequate weight which can
lead to a secondary failure in height growth.
What is noted about intrinsic shortness growth rates?
Growth rates are paralleled to normal ones
i.e start and finish shorter but at the same rate
What is delayed growth?
The growth rates are slow for age and puberty is delayed
but then final height is normal
What is attenuated growth?
Aquired pathological disorder where growth is rapid and finishes at a very young age therefore the individual is short
What is the pattern for intrinsic tallness?
Tall Normal Bone age
What is advanced growth?
Faster initial growth rates
Starts puberty early
Ends up at average height
What happens in precocious puberty?
Starts puberty very early and ends up short as an adult, although very tall teenager
Write some notes on normal variant short stature;
• Normal height velocity:
– Familial short stature
– Constitutional delay of growth and development
> 95% of children who present with short stature
NORMAL HEIGHT VELOCITY
What may cause proportional pathological short stature?
• Proportionate:
- IUGR • Syndromes • Chronic illness • Psychosocial deprivation • Growth Hormone Deficiency
What may cause disproportionate pathological short stature?
• Disproportionate:
Syndromes (Turner’s (45 XO, and variations)
- Hypothyroidism
- Skeletal dysplasias
