Anterior Pituitary

Question 1

what is the most abundant cell type anterior pituitary

Answer 1

somatotropes

Question 2

what hormones make up glycoprotein family

Answer 2

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

Question 3

glycoprotein family (composition)

Answer 3

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

Question 4

member of glycoprotein family use what signaling pathway

Answer 4

cyclic AMP signaling pathway (Gs)

Question 5

what hormones are members of the somatomammotropin family

Answer 5

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

Question 6

member of the somatomammotropin family have what type of protein structure

Answer 6

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

Question 7

what hormones are in the proopiomelanocortin family

Answer 7

ACTH

Question 8

about half the GH in circulation is what

Answer 8

bound to GH binding protein

Question 9

GH binding protein has the same molecular structure as what

Answer 9

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

Question 10

GH (direct actions)

Answer 10

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

Question 11

what induces most of the growth promoting factors of GH

Answer 11

IGF-1

Question 12

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

Answer 12

“diabetogenic” effects

Question 13

net result of the metabolic actions of GH

Answer 13

promote fat mobilization and utilization (lipolysis)

conserve blood carbohydrate

Question 14

how does GH conserve blood carbohydrate

Answer 14

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

Question 15

GH has what effect on circulating free fatty acid levels

Answer 15

increases them

Question 16

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

Answer 16

increases chondrocyte proliferation in cartilage growth plate

Question 17

proliferation of what is responsible for bone length growth

Answer 17

chondrocyte

Question 18

proliferation of what is responsible for bone width growth

Answer 18

osteoblastic progenitor cells

Question 19

GH has what net effect on soft tissue

Answer 19

to increase lean body mass

Question 20

how does GH increase lean body mass

Answer 20

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

Question 21

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

Answer 21

decreases as amino acids are converted to proteins

Question 22

exogenous GH does what to body fat

Answer 22

reduces body fat by mobilizing fat stores and decreasing fat deposition

Question 23

GH increases the mass of what organs

Answer 23

liver and spleen

Question 24

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

Answer 24

cytokine receptor family

JAK/STAT pathway

Question 25

GH receptor has what kind of catalytic activity

Answer 25

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

Question 26

janus kinase family (JAK) is what

Answer 26

receptor associated tyrosine kinase

Question 27

GH binding to receptor does what

Answer 27

induces receptor dimerization

Question 28

GH has how many binding sites and why

Answer 28

2 in order to bind 2 different receptors and cause dimerization

Question 29

receptro dimerization of GH receptor allows for what

Answer 29

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

Question 30

phosphorylated JAKs on the GH receptor do what

Answer 30

phosphorylate the GH receptor

Question 31

how does STAT get phosphorylated

Answer 31

dock to phosphotyrosine residues on GH receptor ad JAK phosphorylates them

Question 32

Phosphorylated STAT proteins do what

Answer 32

form dimers and migrate to nucleus where they activate gene transcription

Question 33

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

Answer 33

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

Question 34

local production of IGF-1 is important for what

Answer 34

mediating many of the action of GH

Question 35

what expresses receptors for both GH and IGF-1

Answer 35

chondrocytes in epiphyseal plate

Question 36

circulating IGF-1 is tightly bound to what

Answer 36

IGF binding proteins (IGFBP)

Question 37

IGFBPs (function)

Answer 37

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

Question 38

at high concentrations IGF-1 will mimic what

Answer 38

actions of insulin

Question 39

what IGFBP has highest affinity for IGFs

Answer 39

IGFBP-3

Question 40

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

Answer 40

IGF IGFBP-3 acid-labile subunit (ALS)

Question 41

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

Answer 41

IGFBP

Question 42

what happens to IGF-1's affinity to IGFBP

Answer 42

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

Question 43

the IGF-1 receptor is what type of receptor

Answer 43

receptor tyrosine kinase

Question 44

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

Answer 44

Ras/Map kinase signaling pathway

Question 45

target cells for IGF

Answer 45

``` fibroblasts chondrocytes osteoblasts adipocytes muscle cells ```

Question 46

name some specific effects of IGFs

Answer 46

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

Question 47

GHRH stimulates what and how

Answer 47

synthesis and release of GH via cAMP and PKA

Question 48

PKA has what effect on GH and GHRH

Answer 48

induces transcription og GH and GHRH receptor

Question 49

what inhales the action of GHRH on GH release

Answer 49

ghrelin

Question 50

somatostatin (what does it do in ratlin to GH)

Answer 50

blocks basal and GHRH-stimulated GH release

Question 51

somatostatin (how does it work)

Answer 51

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

Question 52

short feedback of GH secretion

Answer 52

GH inhibits GHRH secretion form hypothalamus and stimulates somatostatin release

Question 53

long feedback of GH secretion

Answer 53

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

Question 54

in what type of pattern is GH released

Answer 54

secretory pulses in circadian pattern of release

Question 55

large burst of GH occurs when

Answer 55

1-2 hours after onset of deep sleep

Question 56

conditions that stimulate GH secretion

Answer 56

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

Question 57

conditions that inhibit GH secretion

Answer 57

hyperglycemia | elevated levels of free fatty acids

Question 58

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

Answer 58

GH significantly elevated | total IGF-1 levels are unchanged

Question 59

what happens to free IGF-1 after 24 hour fast

Answer 59

decline by 50%

Question 60

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

Answer 60

GH levels are elevated | circulating IGF-1 levels are decreased

Question 61

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

Answer 61

hepatic IGF production requires adequate neutron and insulin

Question 62

when is daily pituitary output of GH highest

Answer 62

adolescent growth spurt

Question 63

what happens to GH and IGF levels with age

Answer 63

GH decreases steadily after 3rd decade | IGF declines in proportion to GH output