Pediatric Growth and Development Flashcards
during growth plate growth, chondrocytes start in the ____ zone and migrate towards the ____
during growth plate growth, chondrocytes start in the GERMINAL zone and migrate towards the SHAFT
where is the primary/ maximal site of bone growth?
hypertrophic zone within growth plate
what are the zones of the growth plate?
- germinal zone (closest to epiphysis)
- proliferative zone
- hypertrophic zone - area of maximal growth
- zone of endochondral ossification
- zone of Ranvier (closest to shaft/ diaphysis)
in the first year of life, what is the primary driver of growth?
thyroid hormone and GH-independent IGF-1, insulin
growth hormone becomes crucial after first year of life
what is the role of estrogens in growth plate maturation?
estrogens stimulate GH secretion and also promote growth plate “closure” (transition to bone)
this is why males tend to be taller, because there is more estrogen in females
what are 3 tools used to asses a child’s growth?
- growth charts/ velocity - is child growing at an appropriate rate for their age?
- midparental height - generates rough estimate of genetic height potential - is growth appropriate for their family?
- bone age of left hand/wrist - estimates pace of skeletal development - is growth appropriate for maturity?
what is the “rule of 5’s” of growth velocity in early development?
fetal: up to 100cm/year at peak
at birth: 50cm/year
0-1: 25cm/year
1-4: 10-15cm/year
4+: 5cm/year
growth velocity is most important physiologic metric for growth
what is “channeling down” growth variation?
benign variation in growth - most children change height percentiles in first 2 years of life as their own genetic potential becomes more influential than factors from their intrauterine environment (maternal and environmental factors)
what is “constitutional delay” of growth and puberty?
benign variation in growth - “late bloomers”
benign because they end up catching up
what is considered familial short stature?
benign variation in growth - less than 50th percentile, but growth is within expectations given family heights
initial birth length is often normal, but slows to low-normal growth velocity that is maintained throughout childhood
how is growth hormone deficiency measured/monitored, besides measuring hormonal levels?
growth failure after early infancy (6+ months old)
have low growth velocity for age, predicted adult height is below genetic potential (family), dropping height percentiles (2+)
however weight is preserved (normal or increased weight:height ratio)
Laron syndrome
defect in growth hormone receptor, causing growth hormone resistance
presents like GH deficiency, but with high or normal GH levels
what gene defect in Turner syndrome is responsible for causing short stature?
SHOX gene haploinsufficiency