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SF4 Exam 2 > Anterior Pituitary > Flashcards

Anterior Pituitary Flashcards

1
Q

what is the most abundant cell type anterior pituitary

A

somatotropes

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2
Q

what hormones make up glycoprotein family

A

FSH
LH
TSH
hCG (human chorionic gonadotropin)- placental glycoprotein hormone

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3
Q

glycoprotein family (composition)

A

two subunits held together by non-covalent bonds
alpha subunit identical in all
beta subunit unique for each

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4
Q

member of glycoprotein family use what signaling pathway

A

cyclic AMP signaling pathway (Gs)

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5
Q

what hormones are members of the somatomammotropin family

A

GH
PRL
hGH-v (placental GH)
hCS (chorionic somatomammotropin)/ hPL (placental lactogen)

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6
Q

member of the somatomammotropin family have what type of protein structure

A

single chain proteins containing intrachain disulfide bridges
2 for GH and hCS
3 for PRL

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7
Q

what hormones are in the proopiomelanocortin family

A

ACTH

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8
Q

about half the GH in circulation is what

A

bound to GH binding protein

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9
Q

GH binding protein has the same molecular structure as what

A

external portion of GH receptor (formed by cleavage of receptor)

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10
Q

GH (direct actions)

A

IGF-1 production
lipolysis by adipocytes
amino acid uptake and protein synthesis by liver

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11
Q

what induces most of the growth promoting factors of GH

A

IGF-1

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12
Q

GH has what type of metabolic effects with respect to carbohydrate and lipid metabolism

A

“diabetogenic” effects

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13
Q

net result of the metabolic actions of GH

A

promote fat mobilization and utilization (lipolysis)

conserve blood carbohydrate

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14
Q

how does GH conserve blood carbohydrate

A

inhibits glucose uptake by skeletal muscle and adipose tissue
decreases sensitivity of these tissues to insulin

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15
Q

GH has what effect on circulating free fatty acid levels

A

increases them

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16
Q

in a hypopituitary subject GH administration does what (in regards to skeletal growth)

A

increases chondrocyte proliferation in cartilage growth plate

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17
Q

proliferation of what is responsible for bone length growth

A

chondrocyte

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18
Q

proliferation of what is responsible for bone width growth

A

osteoblastic progenitor cells

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19
Q

GH has what net effect on soft tissue

A

to increase lean body mass

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20
Q

how does GH increase lean body mass

A

stimulates uptake of amino acids and protein synthesis and inhibits proteolysis in skeletal muscle and other GH-responsive tissues

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21
Q

in the presence of GH what happens to blood urea and urinary nitrogen excretion

A

decreases as amino acids are converted to proteins

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22
Q

exogenous GH does what to body fat

A

reduces body fat by mobilizing fat stores and decreasing fat deposition

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23
Q

GH increases the mass of what organs

A

liver and spleen

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24
Q

GH receptor is what kind of receptor and works via what pathway

A

cytokine receptor family

JAK/STAT pathway

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25
Q

GH receptor has what kind of catalytic activity

A

no intrinsic catalytic activity instead intracellular kinase is tightly bound to cytoplasmic domain

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26
Q

janus kinase family (JAK) is what

A

receptor associated tyrosine kinase

27
Q

GH binding to receptor does what

A

induces receptor dimerization

28
Q

GH has how many binding sites and why

A

2 in order to bind 2 different receptors and cause dimerization

29
Q

receptro dimerization of GH receptor allows for what

A

2 JAKs to come into close enough contact to phosphorylate each other

30
Q

phosphorylated JAKs on the GH receptor do what

A

phosphorylate the GH receptor

31
Q

how does STAT get phosphorylated

A

dock to phosphotyrosine residues on GH receptor ad JAK phosphorylates them

32
Q

Phosphorylated STAT proteins do what

A

form dimers and migrate to nucleus where they activate gene transcription

33
Q

JAK 2 allows GH to what (in terms of signaling pathways)

A

active additional intracellular signaling pathways b/c JAK 2 phosphorylates more than one signaling protein

34
Q

local production of IGF-1 is important for what

A

mediating many of the action of GH

35
Q

what expresses receptors for both GH and IGF-1

A

chondrocytes in epiphyseal plate

36
Q

circulating IGF-1 is tightly bound to what

A

IGF binding proteins (IGFBP)

37
Q

IGFBPs (function)

A

provide circulating reservoir of IGF
increase circulatory half life
modulate bioavailability of IGF

38
Q

at high concentrations IGF-1 will mimic what

A

actions of insulin

39
Q

what IGFBP has highest affinity for IGFs

A

IGFBP-3

40
Q

most IGF in blood is transported in a large molecular weight complex composed of what

A

IGF
IGFBP-3
acid-labile subunit (ALS)

41
Q

IGF-1’s affinity is greater for IGF receptor or IGFBP?

A

IGFBP

42
Q

what happens to IGF-1’s affinity to IGFBP

A

when IGFBP binds to surface of target cell or is degraded by IGFBP proteases the affinity decreases

43
Q

the IGF-1 receptor is what type of receptor

A

receptor tyrosine kinase

44
Q

growth promoting and mitogenic actions of IGF-1 are done through what pathway

A

Ras/Map kinase signaling pathway

45
Q

target cells for IGF

A 
fibroblasts
chondrocytes
osteoblasts
adipocytes
muscle cells
46
Q

name some specific effects of IGFs

A

stimulation of DNA, RNA and protein synthesis
cell proliferation
insulin-like effects on adipose tissue and muscle

47
Q

GHRH stimulates what and how

A

synthesis and release of GH via cAMP and PKA

48
Q

PKA has what effect on GH and GHRH

A

induces transcription og GH and GHRH receptor

49
Q

what inhales the action of GHRH on GH release

A

ghrelin

50
Q

somatostatin (what does it do in ratlin to GH)

A

blocks basal and GHRH-stimulated GH release

51
Q

somatostatin (how does it work)

A

Gi

inhibits adenyl cyclase and activated K+ channels to hyper polarize the cell membrane

52
Q

short feedback of GH secretion

A

GH inhibits GHRH secretion form hypothalamus and stimulates somatostatin release

53
Q

long feedback of GH secretion

A

IGF-1 inhibits GH secretion by working on the pituitary of hypothalamus

54
Q

in what type of pattern is GH released

A

secretory pulses in circadian pattern of release

55
Q

large burst of GH occurs when

A

1-2 hours after onset of deep sleep

56
Q

conditions that stimulate GH secretion

A

exercise
stress
sleep
protein meal or IV infusion with certain amino acids (arginine)
postprandial (insulin induced) hypoglycemia
sex steroids
ghrelin

57
Q

conditions that inhibit GH secretion

A

hyperglycemia

elevated levels of free fatty acids

58
Q

after 48hour fast what would GH and total IGF-1 plasma levels be like

A

GH significantly elevated

total IGF-1 levels are unchanged

59
Q

what happens to free IGF-1 after 24 hour fast

A

decline by 50%

60
Q

during starvation and protein-calorie malnutrition what happens to circulating GH and IGF-1 levels

A

GH levels are elevated

circulating IGF-1 levels are decreased

61
Q

why can GH levels be elevated while IGF-1 levels decreased

A

hepatic IGF production requires adequate neutron and insulin

62
Q

when is daily pituitary output of GH highest

A

adolescent growth spurt

63
Q

what happens to GH and IGF levels with age

A

GH decreases steadily after 3rd decade

IGF declines in proportion to GH output

SF4 Exam 2 (13 decks)

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