176 growth and development Flashcards
(16 cards)
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
secondary growth disorders (endocrine, malnutrution)
is linear growth rate normal?
secondary to another problem - malnutrution, chronic disease, endocrine issues
no - delayed skeletal age (younger) –> indicates potnetial for additional growth
endocrine issues - hypothroidism, cushing’s syndrome (usually iatrogenic), IGF deficiency (anywhere along the axis of hypo - pit, GHRH receptor mutation, IGF resistance)
