Lecture 17: Growth Hormone

Question 1

What are the primary regulators of GH release (stimulation and inhibition)

Answer 1

Stimulation: GHRH
Inhibition: somatostatin

Question 2

What is the long term controller of GH secretion

Answer 2

Long term nutritional state, particularly that of protein nutrition

Question 3

What does the hypothalamus signal to in HPL axis

Answer 3

Anterior pituitary somatotrophs

Question 4

How does GHRH stimulate release of GH

Answer 4

Hypothalamus releases GHRH which binds Gs protein, activates AC—> cAMP—>PKA—> CREB which activates expression of PIT1 gene

Question 5

What does PIT1 gene regulate

Answer 5

Expression of GH and GH-receptors

Question 6

What type of hormone is growth hormone

Answer 6

Peptide

Question 7

Where is GHRH secreted from in hypothalamus

Answer 7

Medial preoptic area and arcuate/infundibular nucleus

Question 8

Emotion, stress and trauma ___ release of GHRH

Answer 8

Inhibit

Question 9

Catecholamines, dopamine and serotonin ___ release of GHRH

Answer 9

Increase

Question 10

Does GH increase or decrease after exercise, food restriction and sleep

Answer 10

Increases

Question 11

Why is GH hormone not a good indicator of pituitary somatotroph function

Answer 11

Released in pulsatile bursts and levels fluctuate throughout day

Question 12

What is the indirect effect of GH

Answer 12

Stimulates liver to promote growth positive effects via IGF-1

Question 13

What are the direct effects of GH

Answer 13

Intermediary fuel metabolism via binding the growth hormone receptors in tissue

Question 14

What mechanism regulates release of GH

Answer 14

Negative feedback from GH and IGF-1 to hypothalamus and pituitary to stop release of GHRH and increase GHIH/somatostatin

Question 15

How does growth hormone effect blood glucose

Answer 15

Increase:
Decrease glucose uptake by muscles
Increase glucose sparing

Question 16

does growth hormone increase or decrease lipolysis

Answer 16

Increase lipolysis

Question 17

How does growth hormone effect amino acids

Answer 17

Increase uptake into cell, decrease blood AA

Question 18

How does growth hormone effect muscle protein

Answer 18

Increase protein synthesis
Decrease protein degradation
Increase DNA and RNA synthesis

Question 19

Is GH levels increased or decreased during hypoglycemia

Answer 19

Increased

Question 20

When protein is the main food source what happens to GH, IGF and insulin levels

Answer 20

Increase all 3

Question 21

GH facilitates insulin action to do what in a high protein diet

Answer 21

Promote growth and protein anabolism

Question 22

In a high protein diet what is the effect on caloric storage

Answer 22

Little to no change in caloric storage

Question 23

In a high carbohydrate diet what happens to GH, IGF-1 and insulin levels

Answer 23

Decrease GH
No change to IGF-1
Increase insulin

Question 24

Hyperglycemia ___ GH while insulin is ____

Answer 24

Suppress GH
Insulin is released to promote storage of carbs

Question 25

A high carb diet has what effect on caloric storage

Answer 25

Increased caloric storage

Question 26

What is the effect of fasting on GH, IGF-1, and insulin

Answer 26

Increase GH Decrease IGF-1 and insulin

Question 27

Fasting causes hypoglycemia therefore ____GH release

Answer 27

Stimulating release of GH

Question 28

GH _____ lipolysis, ___ hepatic gluconeogenesis and ___ peripheral glucose uptake

Answer 28

Enhances lipolysis Increases hepatic gluconeogenesis Decreases peripheral glucose uptake

Question 29

How does fasting effect protein anabolism and growth

Answer 29

Decreases both

Question 30

What is the effect of fasting on caloric storage

Answer 30

Increases caloric mobilization

Question 31

When is Ghrelin signaling necessary to stimulate GH release

Answer 31

Ghrelin is necessary to trigger GH during nutritional deprivation to prevent hypoglycemia and death

Question 32

Hypoglycemia from fasting stimulates GH secretion what are the effects of GH under these conditions

Answer 32

Catabolic and glucose sparing Stimulate lipolysis Stimulate gluconeogenesis Inhibit glucose uptake

Question 33

What happens to insulin, glucagon and cortisol levels during fasting

Answer 33

Increase glucagon and cortisol Decrease insulin

Question 34

An increase in GH and cortisol promotes synthesis of

Answer 34

IGF-BP3

Question 35

What does IGF-BP3 do

Answer 35

Limits bioavailability of IGF-1 to tissues

Question 36

How does ghrelin promote GH release

Answer 36

Stimulatory effect on pituitary somatotrophs

Question 37

How does ghrelin effect the liver

Answer 37

Increases glucogenonesis

Question 38

GH activates growth primarily via ___

Answer 38

IGF-1

Question 39

What two hormones promote long bone growth only as long as epiphyseal plate remains open

Answer 39

GH/IGF-1

Question 40

Pubertal growth correlates well with ____plasma levels

Answer 40

IGF-1

Question 41

At end of adolescence ___ induce ossification of epiphyseal plates

Answer 41

Sex steroids

Question 42

What is gigantism

Answer 42

Increased linear growth due to excessive stimulation of epiphyseal plates (excess GH)

Question 43

What is acromegaly

Answer 43

Increased growth after fusion of epiphyseal plates

Question 44

How has high plasma IGF-1: standard or miniature poodle

Answer 44

Standard

Question 45

What are some symptoms of acromegaly

Answer 45

Bone and soft tissue deformities, enlarged feet, viscera size increases, thick skin, increased protein and decreased body fat, vision changes and headaches, elevated BG and propensity for type II, PD/PU, heart failure

Question 46

What are some physical signs of acromegaly

Answer 46

Increase interdental spaces and macroglossia

Question 47

What are 2 methods of acromegaly diagnosis

Answer 47

1. IFG-1: elevated 2. Pituitary MRI- somatotrope adenoma

Question 48

What other hormone works synergistically with GH to promote growth in children

Answer 48

Thyroid hormone

Question 49

How does insulin and GH work together to promote growth

Answer 49

Insulin promotes protein synthesis Insulin resembles IGF-1 so may bind receptors

Question 50

Glucocorticoid and GH synergism

Answer 50

Required for proper GH signaling but in excess will be inhibited by somatostatin

Question 51

In males, what hormone stimulates bone growth during puberty

Answer 51

Testosterone

Question 52

What hormone accelerates the closure of epiphyseal plates in males at end of puberty

Answer 52

Testosterone

Question 53

in males what two hormones enhance IGF-1 secretion from liver

Answer 53

Testosterone and growth hormone

Question 54

Testosterone stimulates release of what hormone from pituitary

Answer 54

GH

Question 55

What hormone promotes early pubertal growth spurt in women

Answer 55

DHEA

Question 56

What hormone in women attenuates GH released IGF-1 secretion from liver

Answer 56

Estrogen

Question 57

Why is the key hormone for increasing metabolic needs prior to tissue accumulation

Answer 57

Thyroid hormone

Question 58

T3/T4 permit release of ___ from pituitary

Answer 58

GH

Question 59

What are the growth effects of thyroid hormone

Answer 59

Facilitates linear growth of bone, increase activity of cartilage chondrocytes

Question 60

What hormone stimulates bone remodeling

Answer 60

T3

Question 61

What hormone is required for tooth development and eruption

Answer 61

Thyroid

Question 62

What hormone is involved in growth and maturation of epidermis, hair follicles and nails

Answer 62

Thyroid

Question 63

T3 activates genes related to

Answer 63

Bone growth and turnover

Question 64

What are the two growth factors (bone resorption) activated by T3

Answer 64

IL-6 and PGE2

Question 65

What receptor is activated by T3 for bone formation

Answer 65

IGF-1 receptor

Question 66

What are the positive effects of glucocorticoids on GH signaling

Answer 66

Induce GH expression, induce GHRH receptor on somatotrophes, increase ghrelin receptors on somatotrophs

Question 67

What are the negative effects of excess glucocorticoids on GH signaling

Answer 67

Increase somatostatin, decrease expression of GH receptor, Cushing’s

Question 68

How does stress affect growth hormone secretion

Answer 68

Decreases GH secretion because although cortisol levels increase GH release if they pass healthy level they will suppress GH

Question 69

How might different levels of stress alter growth

Answer 69

High stress, decrease growth

Question 70

How does cortisol stimulate both GH and somatostatin

Answer 70

Healthy amounts of cortisol will stimulate GH, excessive amounts of GH will stimulate somatostatin