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physiology of growth hormone Flashcards

1
Q

what is the definition of growth?

A

1- protein synthesis

2- Lengthening of long bone

3- Increase in number and size of cells in SOFT tissue

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2
Q

what is mainly responsible for growth in CHILDHOOD?

A

Growth hormones

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3
Q

what is the other name of growth hormone?

A

somatotropin

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4
Q

what is mainly responsible for growth in Adulthood?

A

Steroids take over growth

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5
Q

when do the 2 growth spurts in life happen?

A

Postnatal period –> 1st year of life

After year 1 velocity of growth will decrease and it will enter plateau until puberty

Pubertal period –> late teens

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6
Q

what are the parameters we care about in first year of life?

A

1- Height

2- Weight ( around 10 kg)

3- Head circumference

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7
Q

what are the important stuff for growth?

A

Growth hormone

nutritions

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8
Q

what is main cause of dwarfism?

A

can be related to nutrition deficiency

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9
Q

which structures keep growing even after pubertal period?

A

membranous bones –> Cranial , vertebra, frontal, jaw

THESE ARE ONES AFFECTED IN ACROMEGALY BECAUSE IT HAPPENS IN AFTER ADOLESCENSE AND THEY ARE CONTIUOUS GROWING BONES

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10
Q

how is growth monitored ?

A

well baby clinic –> we check the height , weight, head circumference

After 2 years –> focus on weight and height

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11
Q

which hormones are the most important for growth ?

A

Growth hormone –> PRIMARIRLY

insulin ( insulin like growth factor )

Thyroid hormone

Sex hormones

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12
Q

what is thyroid hormone involved in that makes it related to growth?

A

synaptogenesis –> if deficit –> short stature and mental retardation

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13
Q

what stimulates growth hormone release?

A

Growth hormone releasing hormone –> stimulates anterior pit somatotropes to release Growth hormone

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14
Q

what will the growth hormone do?

A

1- Stimulate liver to release insulin like growth hormone 1 –> IGH1 will work on bones and muscles

2- stimulate stomach to release ghrelin ( hunger )

3- Lipolysis and elevate blood glucose

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15
Q

how is Growth hormone inhibited?

A

1- Hypothalamus release Growth hormone inhibitory hormone

2- Growth hormone inhibit the release of itself by negative feedback

3- Insulin like growth hormone 1 will cause the release of GHIH from hypothalamus and inhibit GHRH –> overall inhibit growth hormone

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16
Q

what would the ghrelin do in regulation of growth hormone?

A

ghrelin is released by the stomach to stimulate hunger

1- it will stimulate somatotropes to release more GROWTH HORMONE

2- it will inhibit Growth hormone inhibitory hormone (GHIH) –> MORE GROWTH HORMONE

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17
Q

what is the % of somatotrope in anterior pit?

A

30-40% of cells

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18
Q

in the net result which hormones will inhibit gh and which will increase gh?

A

Growth hormone will inhibit itself by negative feedback

GHRH will increase GH release

GHIH will inhibit GH release

IGF-1 will inhibit GHRH and stimulate GHIH –> inhibitory

Ghrelin will increase GHRH and GH and inhibit GHIH

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19
Q

what is the other name of GHRH ?

A

somatoliberin

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20
Q

in what way GH is secreted?

A

pulsatile release pattern

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21
Q

when does the level of growth hormone increase?

A

Sleep ( increases in the first half and decline in the second )

Exercise

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22
Q

in which period of life you will have the most amount of GH?

A

during childhood you will have the maximum amount of GH then it declines

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23
Q

what could lead to increase level of growth hormone?

A

starvation and malnutrition cuz of hypoglycemia

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24
Q

where is growth hormone metabolized ?

A

Liver

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25
what is the half life of growth hormone?
6-20 minutes
26
how will growth hormone do its function when it has short half life?
it will release insulin growth hormone 1 from the liver then this will do most of the job and it has long half life
27
how is growth hormone traveling in the circulation?
50% of the circulating pool of growth hormone activity is in THE BOUND FORM --> inactive and long half life binds to growth hormone binding globulin
28
what are the stimulants for growth hormone release?
stress trauma Sleep malnutrition -> it increases protein synthesis hypoglycemia --> it increases glucose level in the blood and lipolysis
29
what is kwashiorkor ?
condition of extreme malnutrition and protein deficiency
30
what happens in kwashiorkor?
very high levels of growth hormone
31
what is the role of growth hormone in kwashiorkor?
growth hormone will try to overcome the stress and malnutrition by lipolysis and increasing glucose level
32
how do you bring back growth hormone levels back to normal in kwashiorkor?
you need to give protein treatment if you give something else it is not gonna help YOU HAVE TO GIVE PROTEIN TO TREAT THE ELEVATION
33
why is protein treatment the only way to bring down growth hormones level back to normal in kwashiorkor?
because protein deficiency is a great stimulus to increase growth hormone
34
what is the effect of hypoglycemia on growth hormone?
acute growth hormone release
35
what are the factors that lead to increases level of growth hormone secretion?
Hypoglycemia ( gh will increase glucose ) Decreased free fatty acid ( Gh will cause lipolysis ) Fasting ( malnutrition ) Prolonged caloric deprivation stress Exercise puberty ( second growth spurt at late teens ) Androgens and estrogens ( we said steroids are responsible for growth ) Sleep
36
what factors that inhibit the release of growth hormone?
Somatostatin increased level of glucose Increased amount of free fatty acid caused by lipolysis from gh so negative feedback somatomedins ( IGF1 --> inhibits GHRH and stimulates GHIH ) Growth hormone ( negative feedback ) Cortisol --> cuz it increased the blood lvl of glucose senescence ( Aging )
37
what is the other name of igf-1 ?
Somatomedin C
38
what are the 2 hormones in the hypothalamus responsible for regulating growth hormone?
GHRH GHIH
39
which one is the most potent one?
GHRH
40
which nucleus in the hypothalamus is sensitive for glucose level?
ventromedial nucleus releases GHRH when theres hyperglycemia?
41
in which signaling mechanism does GHRH work with?
Extracellular --> G protein coupled receptor and secondary messenger
42
describe the mechanism of action of GHRH?
GH releasing hormones from hypothalamus -------> Receptors on SOMATOTROPE cells in pituitary ----------> ADENYLATE CYCLASE system activated -----------> Increases in intracellular CAMP --> short and long term effects
43
what are the short term effects of GHRH?
increase in calcium release of GH vesicles
44
what are the long term effects of GHRH?
increase gene transcription Increase in GH synthesis
45
what is the function GHIH?
inhibit GH release from somatotrope cells
46
what are the effects of ghrelin on GH?
bind to somatotroph cells and increase release of GH
47
what the effect of GH in protein metabolism?
- Increase amino acid uptake - Increase protein synthesis
48
what is the role of GH in fat metabolism?
-Triglyceride breakdown in adipocyte --> lipolysis -Release of fatty acids adipose tissues
49
what is the role of GH in carbonhydrate metabolism?
Decrease Carobonhydrate utilization decreases glucose uptake in tissues such as fat and muscles ( why it increases glucose lvl in blood ) increase insulin secretion Increased glucose production by liver ( Diabetogenic effect )
50
What does growth hormone makes the body do in relation to insulin?
body becomes insulin resistant it is why acromegaly and gigantism is associated with diabetes
51
what is the effect of growth hormone on cartilage and bone growth ?
GH stimulates long bones to grow in LENGTH ----? DUE deposition of new cartilage Grow in length by cartilage deposition GH stimulates osteoblasts to deposit new bone on the surface of old bone ----> THICKER THROUGHOUT LIFE UNDER THE EFFECT OF GH Thickening by increased osteoblast deposition
52
how does GH causes bone growth?
via IGF-1 ( somatomedin C )
53
how many types of somatomedin do we have and which one is the most important one?
4 TYPES most common is somatomedin C ( igf1 )
54
how is the concentration of Somatomedin C determined ?
it is determined by the rate of GH secretion
55
where is somatomedin C produced?
in liver in response to GH but could be produced in other locations
56
how does GH produce most of it its effects?
via IGF1 its receptor and structures are similar to those of insulin
57
compare the half life of GH and IGF1?
IGF1 has much longer half life because it binds strongly to binding protein compared to GH
58
what is pygmies of africa and levi lorain dwarf?
deficiency of somatomedin C ( IGF-1 ) even though there's high level of GH in the plasma so GH wont be able to produce most of it is effect because no IGF1
59
what are the 3 conditions related to GH?
Gigantism acromegaly dwarfism
60
How will GH work when injected directly to the JOINT?
it will work via 2 ways when it is in a specific area its stimulates IGF-1 in the specific area it can work by it own ( GH alone )
61
whats the difference between gigantism and acromegaly?
gigantism ---> in childhood before adolescences acromegaly --> adulthood after adolescence
62
what are the causes of dwarfism?
1- Panhypopituitarism ( genralised deficiency of anterior pituitary secretions 2- Hypothalamic dysfunction ( no GHRH ) 3- secretion of inactive growth hormone 4- Failure to form somatomedins ( no IGF1 )--> pygemin of africa or levi lacrain dwarfism 5- Receptor deficiency
63
describe dwarfism?
in general body parts develop in appropriate proportion another ( BODY SHAPE IS NORMAL IT JS SMALL) Rate of the body development is less A person at 20 may have the body development of child 7 of 10 years of age ----> PANHYPOPITUITARRISM ( in case of pituitary defect many hormones are affected including sexual hormones ) insufficient gonadotropic hormones No puberty in one third of these only GH is deficient mature sexually and may reproduce
64
describe african pygmies?
rate of GH secretion is normal or high Congenital inability to synthesize significant amount of IGF-1 length range from 100-120 cm Symmetrical retardation of growth mentally normal ( in thyroid defic --> mental retardation )
65
what is laron syndrome?
similar problem to African pygmies BUT it is mutation of GH receptor therefore Failure of GH to stimulate formation of IGF-1 CUZ NO RECEPTOR
66
how do we treat dwarfism?
growth hormone from human because it is species specific human GH can be synthesized by escherichia coli bacteria as a result of sucessful application of recombinant of DNA technology NOT ORALLY CUZ IT WILL GET DIGESTED
67
what happens when you have excessive growth hormone before adolescence?
Gigantism
68
what are the causes of gigantism?
Excessive production of GH Acidophilic tumors ( Tumor in pit gland )
69
what are the characteristics of gigantism ?
all body tissues including bones grow rapidly heigh increases - 8 feet tall giant
70
What are complications of gigantism?
hyperglycemia --> diabetes mellitus in 10% of patients --> due to insulin resistance caused by GH
71
what could it lead to in case of acidophilic tumor?
panhypopituitarism if it grows excessively --> Destroy the gland --> Death
72
what is the treatment of gigantism?
in case of tumor --> Microsurgical removal of tumor or irradiation of the gland
73
how do we differentiate between diabetes mellitus 1 and 2?
in diabetes mellitus 2 we see obesity
74
what could happen if acidophilic tumor happen after adolescence ?
acromegaly
75
what happens in acromegaly ?
soft tissue grow and thickness of bones increases ( membranous bones only cuz they are continuously growing ) hand and feet size increase nose size increase to twice its normal size Lower jaw protrudes forward forehead slants forward due to enlargement of supraorbital ridges KYPHOSIS ( hunched back )--> due to continuous growth of vertebrae enlargement of many soft tissue organs --> tongue , liver, kindey
76
which hormones induce epiphyseal plate closure ?
sexual hormones
77
what happens normally when you give glucose to a healthy person and compare to acromegaly?
in normal ppl, after eating glucose the GH lvl will drop because increased glucose lvl in acromegaly it will not drop because tumor will keep secreting
78
what happens to GH as you are aging?
GH declines with age
79
which effects does GH have on aging?
has anti ageing actions BUT we dont use GH therapy for aging because of the side effects like cancer, kyphosis, diabetes, etc
80
what are the physical signs of aging ?
increased wrinkling of skin decreased muscle mass and strength
81
what does growth hormone therapy provides?
increased muscle protein deposition ( due to protein synthesis ) more energy ( CUZ increases glucose lvl ) Less fat deposits ( cuz gh causes lipolysis )

physiology :( y2s1 (15 decks)

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