Somatic Growth Flashcards
two periods of rapid postnatal growth occur when
infancy (birth to 2 years)
late puberty
important factors influencing birth size
genetic factors
the placenta
the maternal environment
hormones and growth factors
what relationship is there between placenta and birth size
direct correlation b/w placental weight and birth weight
infants born to women living at higher altitudes tend to be what compared to those born to women living at low altitudes
lower birth weight
infants with varied forms of insulin resistance are what at birth (in terms of size)
very small
infants born to diabetic mothers are what at birth (in terms of size)
high birth weight
IGFs and IGFBPs have what role in fetal growth
essental role in stimulating fetal growth
fetal IGF production (difference from adult IGF)
independent of GH stimulation
IGF-1 levels at term are directly correlated to what
birth weight
what happens to growth rate after birth
decelerates
estimation of boys target height is done using what equation
((moms height+5 inches) + fathers height)/2
estimation of girls target height is done using what equation
((fathers height-5 inches) + moms height)/2
the principal extrinsic regulator of postnatal growth is
adequate nutrition
for adequate nutrition particular importance must be made for what
dietary protein
essential vitamins and minerals
adequate caloric consumption
major cause of short stature world-wide is
malnutrition
what hormones have influence on growth prenatally
IGFs
insulin
what hormone exclusively facilitates postnatal growth
sex steroids
what is the most important hormone involved in promoting postnatal growth
GH
IGF-1 levels peak when in life
pubertal growth spurt
in the absence of GH thyroid hormones do what to growth
do not promote it
in hypothyroid patients what are circulating levels of GH and IGF-1
both have low circulating levels
GH secretion in response to provocative stimuli is diminished in patients with what
hypothyroidism
treatment of hypothyroid with thyroxine does what to plasma GH and IGF-1 levels
both increase
growth spurt at puberty accounts for how much of person stature and is due to what
15% of final stature
due to sex steroids
sex steroids promote what (in terms of growth)
linear growth
maturation and fusion of the epiphyseal growth plate
how do sex steroids increase growth velocity at puberty
stimulating growth hormone
what is the principle hormone that stimulates increase in GH secretion
estradiol (for both males and females)
what is the principle hormone responsible for stimulating growth plate maturation and fusion in both males and females
estradiol (E2)
testosterone can be converted to estradiol via what enzyme
aromatase
defective aromatase gene in boys (what happens)
no growth spurt
androgens are what
potent anabolic steroids
androgens promote what in males during puberty
promote marked increase in muscle mass
testosterone is thought to do what to cortical bone
increase thickness via stimulating periosteal bone expansion
insulin promotes what and inhibits what
promotes anabolism and inhibits protein catabolism
what happens to proteins in absence of insulin
protein breakdown
excessive amounts of glucocorticoids do what to normal growth
interfere- decrease proliferation of chondrocyte
glucocorticoids are what type of agent
potent catabolic agents
in a patient with excess glucocorticoids, removal of excess does what and to what extent
period of increased (catch-up) growth
usually not complete
hypothalamic cause(s) of GH deficiency
GHRH deficiency
target tissue cause(s) of GH deficiency
GH receptor deficiency
inability to produce IGF-1
Laron Dwarfism (cased by what)
deletions or mutations of the gene for GH receptor (type 1)
patients with Laron Dwarfism have what levels of circulating GH
high levels
if a patients does not produce IGF in response to GH administration they may have what
laron dwarfism
type 2 Laron Dwarfism (issue)
post GH receptor defects
consequences of GH deficiency
dwarfism in children
dwarfism (symptoms)
short stature delayed bone development delayed puberty mild obesity tendency toward hypoglycemia
pituitary cause(s) of GH deficiency
somatotrope destruction by a tumor
production of a defective GH molecule
decreased GH production
