Growth Hormone and IGF-1

Question 1

Mediates growth and metabolic functions to include cell proliferation and differentiation, and serum glucose concentrations

Answer 1

Growth Hormone

Question 2

GH is an anabolic hormone. In so doing, it

1. ) Increases
2. ) Lowers

Answer 2

1. ) Urinary nitrogen retention

2. ) Serum urea

Question 3

Target tissues for GH expression express a cell surface receptor consisting of an extracellular ligand binding and cytoplasmic signaling domains. This receptor is the

Answer 3

GH receptor

Question 4

The anabolic actions of GH result from its stimulatory effects on which three things?

Answer 4

1. ) Cellular amino acid uptake
2. ) Increased gene transcription
3. ) De novo protein synthesis

Question 5

GH is an antagonist to the catabolic effects of

Answer 5

Glucocorticoids

Question 6

Promotes lipolysis and this increases the availability of glycerol and free fatty acids as fuel for muscle work

Answer 6

GH

Question 7

During periods of metabolic demand, GH shunts the matabolic pathways from glycogenolysis to the metabolism of FFA into

Answer 7

Acetyl-CoA

Question 8

This increased production of acetyl-CoA is used to produce

Answer 8

ATP

Question 9

GH thus supports the conservation of glycogen stores while decreasing the cellular uptake of

Answer 9

Glucose

Question 10

There are strong relationships between GH and

Answer 10

Glycemic status and insuln

Question 11

GH is the only

Answer 11

Proglycemic hormone

Question 12

Designed to preserve plasma glucose levels by 1) directly blocking glucose uptake by skeletal muscle (promoting insulin resistance), and 2) shunting muscle energy expenditure away from the utilization (oxidation) of glucose to the oxidation of FFA

Answer 12

GH

Question 13

This glucose conservation is of benefit during periods of fasting/starvation when muscle catabolism would be generated by

Answer 13

Glucocorticoids

Question 14

Promote muscle catabolism during periods of fasting/starvation to free up amino acids that can be used to generate ATP

Answer 14

Glucocorticoids

Question 15

Thus acts as a counter modulator to the catabolic actions of glucocorticoids in skeletal muscle

Answer 15

GH

Question 16

GH secretion is suppressed by

Answer 16

Acute hyperglycemia

Question 17

After a meal, insulin is released to promote glucose uptake. The insulin-induced drop in blood glucose in turn stimulates

Answer 17

GH secretion

Question 18

GH tends to slightly raise

Answer 18

Blood glucose levels

Question 19

Should GH remain elevated, we will likely see an increase in the secretion of

Answer 19

Insulin

Question 20

Antagonizes insulin sensitivity in the liver and especially in skeletal muscle

Answer 20

GH

Question 21

This induces an insulin resistant state which maintains

Answer 21

Blood glucose

Question 22

Since elevated GH impairs insulin sensitivity, a subsequent glucose challenge during this insulin resistant period would result in

Answer 22

Hyperinsulinemia

Question 23

Chronic elevation of GH can result in a pathologic condition of

Answer 23

Insulin resistance and accompanying hyperglycemia

Question 24

Work in conjunction under physiologic conditions to stimulate anabolism in bone and muscle tissue

Answer 24

GH and Insulin

Question 25

Insulin and GH each stimulate the cellular uptake of

Answer 25

Amino acids and subsequent protein synthesis

Question 26

A member of the insulin family, and mediates the growth-promoting effect of GH

Answer 26

Insulin-like growth factor (IGF-I)

Question 27

Regulates IGF-I gene transcription

Answer 27

GH

Question 28

Exerts negative feedback on GH secretion

Answer 28

IGF-I

Question 29

Circulating isoforms of truncated IGF-I and GH respectively

Answer 29

IGF binding proteins (IGFBPs) and GH binding proteins (GHBPs)

Question 30

These are produced mainly in the liver, are carrier proteins which extend the half-life of circulating GH and IGF-I, and aid in the delivery of these hormones to target tissues

Answer 30

IGFBPs and GHBPs

Question 31

By extending the half-life of GH, GHBP dampens acute changes in serum GH levels, in part by reducing

Answer 31

Renal clearance of GH

Question 32

Are GH and IGF-I bioactive when they are bound to their respective binding proteins?

Answer 32

No

Question 33

Have been observed with malnutrition, chronic liver disease, and short stature

Answer 33

Low GHBP levels

Question 34

Together, stimulate skeletal muscle growth and proliferation, as well as the growth and deposition of bone

Answer 34

GH and IGF-I

Question 35

In long bones, GH/IGF-I exert mitogenic effects in chondrocytes within the

Answer 35

Epiphyseal cartilages (epiphyseal lengthening)

Question 36

Also promote osteoblast activity, and in so doing, support the deposition of Ca2+ phosphate salts in bone

Answer 36

GH and IGF-I

Question 37

Epiphyseal lengthening has a limited life span, and stops late in adolescence when epiphyseal plates fuse due to rising

Answer 37

Estradiol-17B production

Question 38

The neuroendocrine control of GH secretion resides within the

Answer 38

Hypothalamus and anterior pituitary

Question 39

The ventromedial nucleus of the hypothalamus houses neurons which produce

Answer 39

Growth Hormone Releasing Hormone (GHRH)

Question 40

A stimulatory factor that is secreted into the hypophyseal portal vessels

Answer 40

GHRH

Question 41

GHRH stimulates the production and release of GH by the

Answer 41

Somatotropes (in the anterior pituitary)

Question 42

Express receptors for GHRH, GH secretagogue (stimulatory), dopamine (stimulatory), and somatotroph-release inhibiting factor (SRIF, aka somatostatin, inhibitory), which together represent a few of the central factors that control the secretion of GH

Answer 42

Somatotropes

Question 43

GH secretogues and dopamine stimulate the secretion of

Answer 43

GH

Question 44

What inhibits the secretion of GH?

Answer 44

Somatotroph release inhibiting factor (SRIF)

Question 45

A hormone secreted by the gastric mucosal neuroendocrine cells and the hypothalamus which stimulates GH secretion

Answer 45

Ghrelin

Question 46

Hypoglycemia and depressed serum concentrations of certain amino acids also signal the neuroendocrine release of

Answer 46

GH

Question 47

Acute hyperglycemia lowers GH secretion, however, GH secretion is stimulated by

Answer 47

Chronic Hyperglycemia

Question 48

GH secretion can also be transiently stimulated by high protein meals and the amino acids

Answer 48

Arginine and Lysine

Question 49

In general, metabolic and/or physical stress (to include trauma, hypovolemic shock, sepsis, and exercise) stimulate

Answer 49

GH secretion

Question 50

Will control GH secretion based upon the central (i.e. hypothalamic) receptor isoform that is most activated

Answer 50

Heightened SNS tone

Question 51

Results in stimulation of GH secretion, likely by inhibiting the secretion of somatostatin while increasing seratonin

Answer 51

a2 adrenergic response

Question 52

Are coupled to the release of somatostatin and thus down-regulate GH secretion

Answer 52

B2 adrenoreceptors

Question 53

There is also a circadian rythm for GH secretion, and this results in an increase in serum GH concentrations during the first hours of

Answer 53

Deep (REM) sleep

Question 54

The production of GH is greatest in the child (and through puberty), and following age 20, GH production begins to wane by about

Answer 54

14% per decade

Question 55

By approximately 50-60 years of age. GH secretion can be reduced by 60%. This process is called

Answer 55

Somatopause

Question 56

Has a short half-life; thus, catching peak versus nadir levels is tricky

Answer 56

GH

Question 57

Testing for abnormalities in the GH system relies upon the principles of stimulation and suppression; these are forms of

Answer 57

Endocrine dynamic testing

Question 58

Has been shown to be a fairly reliable marker of GH excess

Answer 58

Serum IGF-I

Question 59

If GH excess is suspected, we rely upon the suppression of GH by glucose as a form of

Answer 59

Suppression testing

Question 60

To conduct this evaluation, the patient is given an oral glucose load (the oral glucose tolerance test, OGGT), and blood GH is drawn at timed intervals after the

Answer 60

Glucose load

Question 61

Failure to lower GH below 2ng/mL shows

Answer 61

Loss of negative feedback (indicates positive test for GH excess)

Question 62

If GH deficiency is suspected, testing relies upon known mechanisms for the stimulation of GH, so called

Answer 62

Stimulation testing

Question 63

Uses insulin tolerance, arginine, GHRH, and exercise to test for GH deficiency

Answer 63

Stimulation testing

Question 64

A disease resulting from the abnormal production of GH/IGF-I

Answer 64

Acromegaly (hypersomatotrophism)

Question 65

Affects roughly equal numbers of men and women and is often diagnosed in the early-mid4th decade of life

Answer 65

Acromegaly

Question 66

Presenting symptoms often include headache and visual field defects (resulting from compression of the neural visual tracts by expanding pituitary mass), and/or a host of reproductive endocrine manifestations ranging from amenorrhea, oligomenorrhea, or galactorrhea to loss of libido and impotence

Answer 66

Acromegaly

Question 67

The pathogenesis of acromegaly most commonly results from a

Answer 67

GH-producing pituitary tumor

Question 68

Disproportionate thickening of bone tissue can occur, and this is especially apparent in the jaw (mandible overgrowth), forehead (frontal skull bossing, cranial ridging), nose, hands, and feet of the adult if there is

Answer 68

Abnormally elevated levels of GH in acromegaly

Question 69

Often times, the first signs of acromegaly are -caused by excess GH targeting essentially all systems with GH and IGF-I receptors

Answer 69

Metabolic and cardiovascular problems

Question 70

Can include enlargement of organs, glands, and soft tissues such as the heart, thyroid, spleen, tongue, liver, and kidneys

Answer 70

Acromegaly

Question 71

Can increase cardiomyocyte contractility by enhancing intracellular Ca2+ -also induces cardiomyocyte hypertrophy

Answer 71

Excess GH

Question 72

GH increases lean body mass by promoting the expansion of total body water (i.e. fluid retention). Second, GH alters vasomotor function, likely due to changes in endothelial structure and function which increase vascular resistance. Thus, GH excess often results in

Answer 72

Hypertension

Question 73

Early on in acromegaly, GH-induced increases in HR raise

Answer 73

Cardiac output

Question 74

Over time, GH can stimulate the formation of -leads to Heart failure

Answer 74

Biventricular hypertrophy

Question 75

Owing to its stimulatory effect on blood glucose levels, chronic GH in acromegaly can lead to impaired

Answer 75

Glucose tolerance, insulin resistance, and diabetes mellitus

Question 76

GH induces volume expansion, resulting in reduced

Answer 76

PRA

Question 77

Increases in total body water may be linked with a GH-directed rise in aldosterone levels that has been observed in

Answer 77

Acromegaly

Question 78

Results from abnormally elevated levels of GH and IGF-I during childhood and puberty -essentially the development of acromegaly in children

Answer 78

Gigantism

Question 79

Often caused by GH secreting tumores and is linked with insulin resistance and hyperglycemia

Answer 79

Gigantism

Question 80

What are two non surgical options to treat gigantism or acromegaly?

Answer 80

1. ) Somatostatin analogue (octreotide) | 2. ) GH-R antagonist (pregvisomant)

Question 81

In about 20-30% of certain somatotroph adenomas, GH secretion can be reduced by

Answer 81

Dopamine agonism

Question 82

Dopamine receptor agonists which can be effective in the management of some forms of acromegaly

Answer 82

Bromocriptine and cabergoline

Question 83

It is believed this mechanism results from a common embryonic lineage of these tumors which couples the mechanism of GH secretion to that of

Answer 83

Prolactin (PRL)

Question 84

Dopamine is a potent inhibitor of

Answer 84

Prolactin (PRL)

Question 85

Realize though that under normal physiologic conditions, dopamine STIMULATES

Answer 85

GH secretion

Question 86

In children, short stature, central obesity, and high pitched voice are signs of

Answer 86

GH deficiency

Question 87

In adults, decreased bone density, central obesity, depression, and an abnormal lipid profile are clues to the presence of -also comes with cardiovascular consequences

Answer 87

GH deficiency

Question 88

Conditions of isolated GH deficiency are very rare. Rather GH deficiency is usually associated with

Answer 88

Hypopituitarism

Question 89

This condition often manifests with signs resembling | that of metabolic syndrome: central obesity, insulin resistance, dyslipidemia, and atherosclerosis

Answer 89

Hypopituitarism

Question 90

When present in children and/or for prolonged duration, GH deficiency can lead to decreased

Answer 90

Left ventricular wall thickness and ejection fraction

Question 91

In additional to its purported performance-enhancing actions, GH has been historically difficult to detect since some exogenous GH preparations have a chemical signature that is virtually indistinguishable from that of

Answer 91

Endogenous GH

Question 92

What is the half-life of GH?

Answer 92

15-20 minutes

Question 93

Data show that while GH replacement does improve physical performance parameters in GH-deficient adults (e.g., muscle mass; strength; and aerobic capacity, VO2max), studies have indicated that it probably has no significant performance-enhancing effect in

Answer 93

Healthy individuals

Question 94

Increased by GH

Answer 94

Lean body mass (LBM)

Question 95

The main performance enhancing benefit of GH

Answer 95

It's lipolytic properties

Question 96

Thus GH is really only beneficial to

Answer 96

Body builders