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Endocrine Physiology > Growth Hormone > Flashcards

Growth Hormone Flashcards

1
Q

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

A

somatotropin
anterior pituitary
polypeptide

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2
Q

what is the effect of GHRH?

A

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

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3
Q

what is the effect of somatostatin?

A

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

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4
Q

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

A

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

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5
Q

describe the secretion of growth hormone

A

released in pulsitile manner with pulses primarily at night

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6
Q

how does GH secretion change during puberty? exercise?

A

larger pulse amplitudes but no increase in number

surge in GH with exercise

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7
Q

how does ritalin affect growth hormone?

A

it disrupts sleep and causes decrease in GH secretion

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8
Q

what is a clinical test to provoke GH secretion?

A

insulin induced hypoglycemia

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9
Q

how do amino acids increase GH release?

A

by decreasing somatostatin release

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10
Q

how is the half life of GH prolonged after release?

A

by associating with GH binding protein

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11
Q

what is GH secretion stimulated by?

A

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

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12
Q

what is GH secretion inhibited by?

A

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

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13
Q

what does obesity do to GH secretion?

A

decreases the number of pulses and the duration of each pulse

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14
Q

from where is GHRH released? what does it do?

A

the arcuate nucleus of the hypothalamus

increases cAMP and Ca> PKA activation

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15
Q

what are the effects of PKA activation with GHRH release?

A

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

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16
Q

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

A

leads to secretion of GH

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17
Q

what hypothalamic neurons synthesize somatostatin? what does it do?

A

the periventricular region

through Gi coupled receptor> lowers cAMP and Ca

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18
Q

what are the major sites of action of GH?

A

bone, liver and adipocyte

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19
Q

what do the receptors for growth hormone activate?

A

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

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20
Q

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

A

CISH

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21
Q

how does GH mediate indirect effects?

A

works through somatomedians like IGF-1

22
Q

what is the effect of GH in the liver?

A

stimulates IGF-1 production and glucose production

23
Q

what is the effect of GH in adipose tissue?

A

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

24
Q

what is the effect of GH in skeletal muscle?

A

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

25
Q

what effect does GH have on the brain?

A

affects mood and behavior

26
Q

what effect does growth hormone have on bone?

A

supports stem cell differentiation into chondrocytes

27
Q

what effect does IGF-1 have in the bone?

A

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

28
Q

besides the liver, where is IGF-1 synthesizes?

A

in the kidney and skin

29
Q

when does GH not induce growth?

A

in animals that lack insulin and in the absence of carbohydrates

30
Q

what are the actions of IGF-1?

A

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

31
Q

what are IGF-1 levels used for?

A

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

32
Q

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

A

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

33
Q

describe the similarities and differences among insulin and IGF receptors

A

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

34
Q

how does IGF correlate to puberty?

A

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

35
Q

what are some causes of GH deficiency?

A

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

36
Q

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

A

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

37
Q

describe laron syndrome

A

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

38
Q

how can laron syndrome be treated?

A

with administration of rhIGF-1 right before puberty

39
Q

what does laron syndrome prevent?

A

cancer, diabetes and acne

40
Q

what is the difference between gigantism and acromegaly?

A

gigantism- had too much GH throughout life

acromegaly- caused by GH secreting adenomas in adulthood

41
Q

what are the symptoms of acromegaly?

A

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

42
Q

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

A

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

43
Q

how is growth factor related to aging?

A

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

44
Q

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

A

restores muscle and reduces fat

side effects: insulin resistence, diabetes, edema and carpal tunnel

45
Q

what is growth hormone treatment approved for?

A

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

46
Q

how do nutritional deficiencies impact growth?

A

decrease levels of IGF-1 and slow growth

47
Q

why does hypothyroidism reduce growth hormone production?

A

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

48
Q

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

A

turner syndrome and down syndrome

49
Q

what is short stature in turner syndrome attributed to?

A

haploinsufficiency of SHOX gene (expressed on hypertrophic zone during childhood

50
Q

describe growth with turner’s syndrome.

A

slower velocity growth during childhood and scant pubertal growth spurt

51
Q

describe the stature of people with extra sex chromosomes

A

they are taller than normal

they don’t go into puberty and don’t fuse their bones- grow longer than normal time

Endocrine Physiology (6 decks)

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