L10 Flashcards
growth factor
what type of hormone is growth hormone?
polypeptide
growth hormone action is mediated by _____
IGF-1
what kind of receptor does GH use?
cytokine receptor
GH is stimulated by _____ and inhibited by _____
GHRH; somatostatin
GH is released by what kind of cell?
somatotrophs in the anterior pituitary
growth hormone is in the same family as _____
prolactin
what type of hormone is prolactin and what does it do?
protein hormone. it regulates breast milk production and lactation in women.
true or false: growth hormone has growth-promoting activity as well as weak prolactin-like lactogenic activity
true
true or false: prolactin has lactogenic activity and growth-promoting activity
false; prolactin has NO growth-promoting activity
Placental lactogen has [strong/weak] lactogenic activity, and [strong/weak] growth-promoting activity
strong; weak
Human placental lactogen is also called ______
human chorionic somatomammotropin (HCS).
factor that inhibits GH secretion
elevated glucose
factors that promote GH secretion
hypoglycemia, exercise, amino acids
true or false: IGF-1 stimulates somatostatin
true
GH is released in a [pulsatile/steady] manner
pulsatile
mechanism of releasing GH
GHRH activates GPCR on anterior pituitary somatotrophs –> adenylate cyclase and PLC –> production of GH and release of GH in vesicles (exocytosis stimulated by Ca)
Actions of growth hormone
Anabolic and Anti-catabolic actions, Increasing protein synthesis, increases FA oxidation, decreasing protein catabolism
what response do all somatostatin receptors cause?
inhibition of adenylyl cyclase
factors stimulating GH (8)
hypoglycemia, protein-rich diet, higher amino acids in blood, exercise, stress, sleep, glucagon, ghrelin
factors inhibiting GH (4)
hyperglycemia, free fatty acids, GH negative feedback of secretion, cortisol excess
IGF-1-dependent effects
protein synthesis, AA transport, muscle mass, bone growth, cartilage growth, nucleic acid synthesis
IGF-1 independent effects
anti-insulin, lipolysis, ketogenesis, hyperglycemia, Na and water retention
Growth Hormone direct effects
stimulates growth (hypertrophy), stimulates cell reproduction (hyperplasia), stimulates cell metabolism (protein synthesis, fat breakdown for energy, glycogen breakdown)
GH stimulates secretion of what hormone(s)?
IGF-1 and IGF-2
GH binding to the GHR dimer results in phosphorylation of ____, which releases the transcription factor ____
Jak2; STAT
effect of GH on blood glucose levels
increases blood glucose levels by counteracting the effects of insulin, promoting gluconeogenesis, and decreasing muscle glucose uptake
makes the body less sensitive to insulin, which can lead to higher blood sugar levels
how do IGF-1 and IGF-2 impact bones?
– Sstimulate chondrocytes (cartilage-forming cells)
– are mitogenic
– stimulate osteoblasts (under PTH and E2)
– stimulate Bone and Cartilage Matrix formation
plasma IGF-1 has a [long/short] half length
long
how is the half-length of plasma IGF-1 useful?
it can serve as a reflection of 24-hour growth hormone secretion
difference between IGF-I and IGF-II
IGF II = fetal growth factor
IGF I = growth factor at all stages
IGF type 1 receptor is similar to the ____ receptor
insulin (tyrosine kinase)
true or false: IGF type 1 receptor only binds IGF-1
false; it binds both but has a lower affinity for IGF-II
type 2 IGF receptor binds _____ and _____
IGF II and mannose-6-phosphate
under what conditions can insulin and IGF-I bind to each other’s receptors?
high concentrations
different physiological roles of insulin and IGF-I accounted
for by ________
cellular distribution of their receptors
IGF-I and II effects on muscle
Increases Muscular proliferation
* +DNA, +RNA, +Protein Synthesis
hypothalamic effects of IGF I and II
Increases SRIH (somatostatin) release and decreases GRH release
what are ways that IGF I and II mimic insulin (4)?
– Stimulate Glucose Uptake
– Stimulate Amino Acid Uptake
– Cross reactions between Insulin and IGF- Receptors
– But, Minimal effectiveness related to Insulin
true or false: IGF-1 levels correspond with body weight
true
true or false: GH secretory capacity corresponds with body weight
false
4 conditions associated with growth hormone (short stature)
– GH deficiency
– Cushing’s syndrome
– Hypothyroidism
– Precocious puberty (accelerated early growth, short adults)
cause of gigantism
oversecretion of somatotrophin, causes overgrowth of skeleton and soft tissues.
describe gigantism
- caused by oversecretion of somatotrophin.
- Body organs, esp. the heart, do not keep up with the growth.
- Sexual dysfunction, other metabolic disturbances, and vision problems (optic atrophy) are common
what is acromegaly?
Complication of gigantism involving
enlargement of the head, hands and feet
_________ is caused by undersecretion of somatotrophin and causes what?
pituitary dwarfism; causes stunting of growth
two causes of hypopituitarism
hypothalamic or pituitary lesions
Hypothalamic lesions (3) causing hypopituitarism
craniopharyngioma, gliomas, teratomas
pituitary lesions (8) causing hypopituitarism
non-secretory adenomas, Sheehan’s syndrome, empty sella syndrome.
radiation, metastatic carcinoma,
ischemia, inflammations & surgical ablation
effects of panhypopituitarism in children
dwarfism & infantilism(retarded physical & sexual development)
the effects of panhypopituitarism in adults are, in order ___ –> ___ –> ___
hypogonadism, hypothyroidism & hypoadrenalism (in this order of
occurrence)
the activity of acromegaly correlates with _____
IGF-I levels
pituitary dwarfism is caused by low ____
IGF levels
anorexia nervosa is caused by high ____ and low ____
high GH and low IGF
what causes Laron syndrome?
Abnormal GH or IGF receptors.
Laron dwarfs have normal or excess plasma GH, but lack liver GH receptors and have low levels of
circulating IGF-1
treatment of Laron syndrome is by what?
IGF-1 (not by GH)
treatment for Isolated Growth Hormone Deficiency (IGHD)?
recombinant human growth hormone (GH)
age of onset for acromegaly vs gigantism
gigantism starts before puberty (before closure of growth plates) and acromegaly starts as an adult
Hormones involved in prenatal growth - placental hormones
placental lactogen, human chorionic thyrotropin, T3, T4, estrogens, progesterone, cortisol, IGF-1, IGF-2
Hormones involved in post-natal growth
growth hormone, IGF-1, IGF-2, T3, T4, estrogens, androgens, glucocorticoids
the skeleton is initially made up of what three components?
– hyaline cartilage
– elastic cartilage
– fibrocartilage
ossification begins in the ____ month of gestation
second
intramembranous vs endochondral ossification
Intramembranous ossification directly converts mesenchymal tissue –> bone, forming flat bones (skull and clavicle).
endochondral ossification happens within hyaline cartilage (mesenchyme –> cartilage –> bone), forming most bones.
