01d: GH and Growth Flashcards
T/F: GH is the single most important hormone required for post-natal growth.
True
T/F: Attainment of adult size is absolutely dependent on GH.
True
GH exerts its effect through mediation by the following chemical messengers: Star the most important
- IGF-I*
- IGF-II
- Somatomedin C
In general, plasma concentrations of (X) reflect availability of (Y) hormone and/or the rate of growth.
X = IGF-I Y = GH
Children whose growth is slower than average have lower concentrations of (X). Administration of (Y) can restore growth to nearly normal.
X = Y = IGF-I
IGF is which type of receptor?
Tyr kinase
T/F: IGF-I stimulates cell growth in cartilage and many other tissues.
False - cell proliferation in those tissues
T/F: IGF-I primarily exerts its effects locally (autocrine/paracrine) and has only minor role in circulation.
True
GH acts directly on (X) to promote IGF-I production. (Y) is the main source of IGF-I in blood.
X = liver and peripheral tissues Y = liver
T/F: Both IGF-I and II are present in blood at relatively high concentrations until adult life (after puberty).
False - high throughout life
T/F: IGF-I and II circulate in blood, bound to IGF binding proteins.
True
GH is secreted (tonically/episodically), with the largest secretion normally associated with (X). List some other factors that induce its secretion.
Episodically (bursts);
X = early hours of sleep
Stress, X, fasting, low glucose
Changes in GH secretion with age primarily reflects changes in (frequency/magnitude) of pulses.
Magnitude
T/F: In the absence of GHRH, GH secretion completely ceases.
True
Plasma IGF-(I/II) plays important role in (stimulating/inhibiting) GH secretion by (stimulating/inhibiting) (X).
I;
Inhibiting;
Inhibiting;
X = GHRH effect on pituitary
(X) growth is stunted in children suffering from unremediated hypothyroidism. This is primarily due to (increase/decrease) in (Y) synthesis.
X = linear;
Decrease;
Y = GH
T/F: During fetal growth, it’s actually thyroid hormones, not GH, that serves as growth-promoting hormone.
False - Insulin!
The (X) organ cell mass is especially important in embryo/fetus, since it produces the growth-promoting hormone during fetal life. This cell mass is determined by locally produced (Y).
X = pancreatic (insulin) Y = IGF-II (predominant IGF in embryo/fetus tissue)
T/F: Insulin concentrations are not as important/effective in maintaining normal growth postnatally.
False - optimal concentrations still required to maintain normal growth
T/F: Unlike IGF-I and II, Insulin doesn’t require plasma-binding protein.
True
When it comes to adolescent growth spurt, (X) hormones are responsible. Specifically, they promote which two key changes?
X = gonadal sex steroids (primarily estrogens)
- Linear growth
- Closure of epiphyses
T/F: Hypogonadal individuals tend to have stunted growth and shorter limbs.
False - opposite (tall with long arms/legs)
T/F: During growth spurt, there isn’t normally a significant change in plasma IGF-I and GH concentrations.
False! Spike in both (responsible for increase in height)
Observations have shown that (estrogens/androgens) are responsible for pubertal growth. This is because (M/F) children lacking (X) don’t experience this growth.
Estrogens;
Both M and F
X = aromatase enzyme
