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