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Physiology > Lecture 17: Growth Hormone > Flashcards

Lecture 17: Growth Hormone Flashcards

1
Q

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

A

Stimulation: GHRH
Inhibition: somatostatin

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2
Q

What is the long term controller of GH secretion

A

Long term nutritional state, particularly that of protein nutrition

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3
Q

What does the hypothalamus signal to in HPL axis

A

Anterior pituitary somatotrophs

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4
Q

How does GHRH stimulate release of GH

A

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

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5
Q

What does PIT1 gene regulate

A

Expression of GH and GH-receptors

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6
Q

What type of hormone is growth hormone

A

Peptide

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7
Q

Where is GHRH secreted from in hypothalamus

A

Medial preoptic area and arcuate/infundibular nucleus

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8
Q

Emotion, stress and trauma ___ release of GHRH

A

Inhibit

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9
Q

Catecholamines, dopamine and serotonin ___ release of GHRH

A

Increase

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10
Q

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

A

Increases

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11
Q

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

A

Released in pulsatile bursts and levels fluctuate throughout day

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12
Q

What is the indirect effect of GH

A

Stimulates liver to promote growth positive effects via IGF-1

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13
Q

What are the direct effects of GH

A

Intermediary fuel metabolism via binding the growth hormone receptors in tissue

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14
Q

What mechanism regulates release of GH

A

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

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15
Q

How does growth hormone effect blood glucose

A

Increase:
Decrease glucose uptake by muscles
Increase glucose sparing

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16
Q

does growth hormone increase or decrease lipolysis

A

Increase lipolysis

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17
Q

How does growth hormone effect amino acids

A

Increase uptake into cell, decrease blood AA

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18
Q

How does growth hormone effect muscle protein

A

Increase protein synthesis
Decrease protein degradation
Increase DNA and RNA synthesis

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19
Q

Is GH levels increased or decreased during hypoglycemia

A

Increased

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20
Q

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

A

Increase all 3

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21
Q

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

A

Promote growth and protein anabolism

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22
Q

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

A

Little to no change in caloric storage

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23
Q

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

A

Decrease GH
No change to IGF-1
Increase insulin

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24
Q

Hyperglycemia ___ GH while insulin is ____

A

Suppress GH
Insulin is released to promote storage of carbs

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25
Q

A high carb diet has what effect on caloric storage

A

Increased caloric storage

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26
Q

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

A

Increase GH
Decrease IGF-1 and insulin

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27
Q

Fasting causes hypoglycemia therefore ____GH release

A

Stimulating release of GH

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28
Q

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

A

Enhances lipolysis
Increases hepatic gluconeogenesis
Decreases peripheral glucose uptake

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29
Q

How does fasting effect protein anabolism and growth

A

Decreases both

30
Q

What is the effect of fasting on caloric storage

A

Increases caloric mobilization

31
Q

When is Ghrelin signaling necessary to stimulate GH release

A

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

32
Q

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

A

Catabolic and glucose sparing
Stimulate lipolysis
Stimulate gluconeogenesis
Inhibit glucose uptake

33
Q

What happens to insulin, glucagon and cortisol levels during fasting

A

Increase glucagon and cortisol
Decrease insulin

34
Q

An increase in GH and cortisol promotes synthesis of

A

IGF-BP3

35
Q

What does IGF-BP3 do

A

Limits bioavailability of IGF-1 to tissues

36
Q

How does ghrelin promote GH release

A

Stimulatory effect on pituitary somatotrophs

37
Q

How does ghrelin effect the liver

A

Increases glucogenonesis

38
Q

GH activates growth primarily via ___

A

IGF-1

39
Q

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

A

GH/IGF-1

40
Q

Pubertal growth correlates well with ____plasma levels

A

IGF-1

41
Q

At end of adolescence ___ induce ossification of epiphyseal plates

A

Sex steroids

42
Q

What is gigantism

A

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

43
Q

What is acromegaly

A

Increased growth after fusion of epiphyseal plates

44
Q

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

A

Standard

45
Q

What are some symptoms of acromegaly

A

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

46
Q

What are some physical signs of acromegaly

A

Increase interdental spaces and macroglossia

47
Q

What are 2 methods of acromegaly diagnosis

A
  1. IFG-1: elevated
  2. Pituitary MRI- somatotrope adenoma
48
Q

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

A

Thyroid hormone

49
Q

How does insulin and GH work together to promote growth

A

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

50
Q

Glucocorticoid and GH synergism

A

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

51
Q

In males, what hormone stimulates bone growth during puberty

A

Testosterone

52
Q

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

A

Testosterone

53
Q

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

A

Testosterone and growth hormone

54
Q

Testosterone stimulates release of what hormone from pituitary

A

GH

55
Q

What hormone promotes early pubertal growth spurt in women

A

DHEA

56
Q

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

A

Estrogen

57
Q

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

A

Thyroid hormone

58
Q

T3/T4 permit release of ___ from pituitary

A

GH

59
Q

What are the growth effects of thyroid hormone

A

Facilitates linear growth of bone, increase activity of cartilage chondrocytes

60
Q

What hormone stimulates bone remodeling

A

T3

61
Q

What hormone is required for tooth development and eruption

A

Thyroid

62
Q

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

A

Thyroid

63
Q

T3 activates genes related to

A

Bone growth and turnover

64
Q

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

A

IL-6 and PGE2

65
Q

What receptor is activated by T3 for bone formation

A

IGF-1 receptor

66
Q

What are the positive effects of glucocorticoids on GH signaling

A

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

67
Q

What are the negative effects of excess glucocorticoids on GH signaling

A

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

68
Q

How does stress affect growth hormone secretion

A

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

69
Q

How might different levels of stress alter growth

A

High stress, decrease growth

70
Q

How does cortisol stimulate both GH and somatostatin

A

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

Physiology (10 decks)

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