Growth Hormone

Question 1

what is another name for growth hormone, where is it produced and what type of hormone is it?

Answer 1

somatotropin
anterior pituitary
polypeptide

Question 2

what is the effect of GHRH?

Answer 2

increases GH gene transcription and release, stimulates GHRH receptor production and stimulates somatostatin release

Question 3

what is the effect of somatostatin?

Answer 3

decreases pulse frequency and amplitude of GH release, no impact on GH synthesis and inhibits GHRH release

Question 4

what is the effect of ghrelin? what is it most important for?

Answer 4

stimulates hunger, acts on growth hormone secretagogue receptor
important for feeding behavior, energy regulation and sleep

Question 5

describe the secretion of growth hormone

Answer 5

released in pulsitile manner with pulses primarily at night

Question 6

how does GH secretion change during puberty? exercise?

Answer 6

larger pulse amplitudes but no increase in number

surge in GH with exercise

Question 7

how does ritalin affect growth hormone?

Answer 7

it disrupts sleep and causes decrease in GH secretion

Question 8

what is a clinical test to provoke GH secretion?

Answer 8

insulin induced hypoglycemia

Question 9

how do amino acids increase GH release?

Answer 9

by decreasing somatostatin release

Question 10

how is the half life of GH prolonged after release?

Answer 10

by associating with GH binding protein

Question 11

what is GH secretion stimulated by?

Answer 11

deep sleep, exercise, sex steroids, hypoglycemia, amino acids, stress, alpha adrenergic agonists and dopamine agonists

Question 12

what is GH secretion inhibited by?

Answer 12

IGF-1, obesity, glucocorticoids, hyperglycemia, free fatty acids, GH, and beta adrenergic agonists

Question 13

what does obesity do to GH secretion?

Answer 13

decreases the number of pulses and the duration of each pulse

Question 14

from where is GHRH released? what does it do?

Answer 14

the arcuate nucleus of the hypothalamus

increases cAMP and Ca> PKA activation

Question 15

what are the effects of PKA activation with GHRH release?

Answer 15

phosphorylation of CREB transcription factor- increasaes transcription of Pit-1
increases GH and GHRH receptor

Question 16

what does the increase in intracellular calcium do with GHRH activation?

Answer 16

leads to secretion of GH

Question 17

what hypothalamic neurons synthesize somatostatin? what does it do?

Answer 17

the periventricular region

through Gi coupled receptor> lowers cAMP and Ca

Question 18

what are the major sites of action of GH?

Answer 18

bone, liver and adipocyte

Question 19

what do the receptors for growth hormone activate?

Answer 19

the JAK/STAT pathway of signal transduction causing receptor dimerization and association of JAK tyrosine kinases JAKs phosphorylate the STATS- dimerize and activate transcription

Question 20

what is a target gene of the GH stimulated JAK/STAT pathway?

Answer 20

CISH

Question 21

how does GH mediate indirect effects?

Answer 21

works through somatomedians like IGF-1

Question 22

what is the effect of GH in the liver?

Answer 22

stimulates IGF-1 production and glucose production

Question 23

what is the effect of GH in adipose tissue?

Answer 23

stimulates release and oxidation of fatty acids especially with fasting
decreased lipoprotein lipases and lipogenesis

Question 24

what is the effect of GH in skeletal muscle?

Answer 24

stimulates amino acid uptake and protein synthesis, cell proliferation and changes muscle fiber distribution
supresses protein degredation

Question 25

what effect does GH have on the brain?

Answer 25

affects mood and behavior

Question 26

what effect does growth hormone have on bone?

Answer 26

supports stem cell differentiation into chondrocytes

Question 27

what effect does IGF-1 have in the bone?

Answer 27

causes proliferation of chondrocytes and maturation. leads to synthesis of ECM and calcification

Question 28

besides the liver, where is IGF-1 synthesizes?

Answer 28

in the kidney and skin

Question 29

when does GH not induce growth?

Answer 29

in animals that lack insulin and in the absence of carbohydrates

Question 30

what are the actions of IGF-1?

Answer 30

stimulates growth and provides negative feedback to the hypothalamus and pituitary to decrease GH secretion

Question 31

what are IGF-1 levels used for?

Answer 31

to screen for growth hormone deficiency because it is reflective of GH levels and more stable.

Question 32

describe the similarities and differences among IGF-1, IGF-2 and insulin.

Answer 32

all three share three domains (A, B and C) C region is cleaved from insulin during processing IGF 1 and 2 have a short D domain IGF 2 not regulated by growth hormone

Question 33

describe the similarities and differences among insulin and IGF receptors

Answer 33

insulin and IGF 1 receptors are heterodimers: S-S bond cytoplasmic portin has tyrosine kinase IGF 2 is single polypeptide chain with no kinase domain

Question 34

how does IGF correlate to puberty?

Answer 34

peak of growth rate corresponds to peak serum levels of IGF 1- both shifted to older age in males

Question 35

what are some causes of GH deficiency?

Answer 35

absence of pituitary stalk, TBI. cranial radiation, function of development, and mutations in GH-1 gene

Question 36

what is the treatment of GH? what are the results?

Answer 36

give exogenous GH (doesn't work in mutation in GH1 gene)- patient does not increase growth above what is attained with normal levels

Question 37

describe laron syndrome

Answer 37

mutation in GH receptor, low IGF-1 concentration, normal or elevated GH, post-natal growth failure

Question 38

how can laron syndrome be treated?

Answer 38

with administration of rhIGF-1 right before puberty

Question 39

what does laron syndrome prevent?

Answer 39

cancer, diabetes and acne

Question 40

what is the difference between gigantism and acromegaly?

Answer 40

gigantism- had too much GH throughout life | acromegaly- caused by GH secreting adenomas in adulthood

Question 41

what are the symptoms of acromegaly?

Answer 41

protrusion of the jaw, macroglossia, enlarged hands and feet, carpal tunnel and reduced strength

Question 42

what are the consequences of GH deficiency in adults? what is it treated with?

Answer 42

reduces strength and bone loss, increases interstitial fat, insulin resistance, clotting factors, CVDand increases anxiety treat with rhGH

Question 43

how is growth factor related to aging?

Answer 43

decreased levels in aging cause loss of muscle mass and increase in interstitial body fat

Question 44

what are the benefits of replacement GH with aging? what are the side effects?

Answer 44

restores muscle and reduces fat | side effects: insulin resistence, diabetes, edema and carpal tunnel

Question 45

what is growth hormone treatment approved for?

Answer 45

GH deficiency, idiopathic short stature, turner syndrome, prader-willi syndrome, chronic renal insufficiency and small for gestational age

Question 46

how do nutritional deficiencies impact growth?

Answer 46

decrease levels of IGF-1 and slow growth

Question 47

why does hypothyroidism reduce growth hormone production?

Answer 47

because there is a thyroid hormone response element upstream of the growth hormone transcriptional start site

Question 48

what are two causes of short stature with normal hormone status?

Answer 48

turner syndrome and down syndrome

Question 49

what is short stature in turner syndrome attributed to?

Answer 49

haploinsufficiency of SHOX gene (expressed on hypertrophic zone during childhood

Question 50

describe growth with turner's syndrome.

Answer 50

slower velocity growth during childhood and scant pubertal growth spurt

Question 51

describe the stature of people with extra sex chromosomes

Answer 51

they are taller than normal | they don't go into puberty and don't fuse their bones- grow longer than normal time