176 growth and development Flashcards
phases of growth
fetal - fast, different mechanism, independent of fetal pituitary; Insulin/IGF is major regulator; need good placenta
infancy/childhood - major regulators GH and T3/4
adolescent - regulated by hypothalamic - pituitary - gonadal axis (sex steroids produce phsyical changes)
major regulator of fetal growth?
insulin - babies born to DM mothers are big becuase glucose crosses placenta and thus kids make more insulin
endocrine regulators (GH, T3/4) dont matter in utero - born normal size BUT IGF-1 does matter
leprechaunism
make insulin but bad receptor - very small in utero
major regulator on growth in infancy and childhood
GH and T3/4
GH affect on bone
increases osteoclast and OB activity - increases endochondral bone formation
promotes epiphyseal growth
what inhibits GH production? how in circulation?
somatostatin
50% bind to GH binding protein = thought to be extracellular part of receptors
when is GH secreted?
at night, during exercise, with food
primary fxn of GH in children?
linear growth via IGF-1 in target tissue
GH action
dimerize –> JAK/STAT pathway –> IGF mRNA production
most important GF for post natal growth?
IGF1 –> binds IGFBP-3 and travels to chondrocytes at epiphseal growth plate along with GH–> both bind receptors (GH causes local IGF production) –> IGF signaling pathway causes proliferative zone to increase cell production
at what point does growth correlate to adult height?
2 years
growth velocity
steady until peak at puberty followed by rapid drop off
abnormal growth warning signs
<3rd percentile
not following genetic potential
crossing percentiles after 2 years
definition of short stature
< -2 SD for age (~3% of kids)
doesn’t mean something is wrong
do kids with primary growth abnormaliites (osteochondrodysplasia, downs, turners, etc) have normal growth rates?
yes, just shorter
normal skeletal age
