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ZA - Endocrine System > Normal Growth and Clinical Aspects > Flashcards

Normal Growth and Clinical Aspects Flashcards

1
Q

Where is GH released from, what does it do, and whats another name for it?

A

Anterior pit. gland
Promotes growth
Somatotrophin

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2
Q

What is somatostatin also called? Whats a good way of remembering this? Where is it released?

A

GH inhibiting hormone

Statin means stasis

Hypothalamus

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3
Q

Can you use GH of non-human species ?

A

No - species specific

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4
Q

What does GH need in order to stim growth?

A

Needs permissive action from thyroid hormones and insulin

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5
Q

What type of hormone is GH, what’s unusual about it?

A

Peptide

Unusual as even though it is a peptide ~50% still bound to carrier proteins

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6
Q

Functions of GH?

A

Growth and development

Maintenance of tissues and energy supply

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7
Q

What controls most of growth in foetal period and 1st 8-10 months of life?

A

Nutritional intake

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8
Q

When does GH become a predominant influence on growth?

A

After ~10 months

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9
Q

What mediates the growth promoting effect of GH?

A

Stimulation of cell size and cell division

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10
Q

What is increase in cell size and division known as ?

A

Hypertrophy and hyperplasia respectively

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11
Q

Is GH’s affect on growth direct or indirect?

A

Indirect

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12
Q

How does GH affect growth?

A

Via the action of an intermediate - IGF-1 (Insulin-like growth factor-1)

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13
Q

What is IGF-I also known as?

A

Somatomedin

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14
Q

How is IGF-1 similar to insulin?

A

Similar structure to pro-insulin
Binds to receptors similar to insulin receptors
Has hypoglycaemic qualities

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15
Q

Where is IGF-1’s hypoglycaemic qualities focused?

A

Muscle tissue

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16
Q

What secretes IGF-1 and when is it released?

A

Liver and many other cell types in response to GH release

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17
Q

What does IGF-1 do?

A

Controls GH release through a neg. feedback loop

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18
Q

What does IGF-2 do?

A

Function limited to foetus and neonate

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19
Q

How does IGF-1 create a feedback loop?

A

Inhibits GHRH and stimulates GHIH/somatostatin

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20
Q

What other feedback loops exist for GH?

A

GH itself acts as a neg. feedback loop

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21
Q

What does GH/IGF-1 do to bone?

A

Turns prechondrocytes –> chondrocytes in the epiphyseal plates
During this differentiation the cells secrete IGF-1 and respond well to IGF-1

IGF-1 then stimulates the differentiating chondrocytes to undergo cell division - making cartilage

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22
Q

When do epipheseal plates close and why? What does this mean?

A

Adolescence

Under influence of sex steroid hormones

No more longitudinal growth (height)

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23
Q

What are some direct effects of GH?

A

Increases gluconeogenesis
Increases lipolysis
Reduces glucose uptake via insulin

Cortisol would cause protein catabolism BUT GH does the opposite (like insulin does)

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24
Q

What does cortisol do to proteins?

A

Stimulates protein catabolsim

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25
Q

Why is GH diabetogenic and what does this word mean?

A

Because it has an anti-insulin effect

It means it increases BG levels

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26
Q

Does insulin or GH increase AA uptake?

A

Both

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27
Q

Does insulin or GH increase glucose uptake?`

A

Just insulin

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28
Q

Does insulin or GH increase protein synthesis?

A

Both do

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29
Q

How is secretion of GH controlled?

A

Via secretions of GHRH and Somatostatin/GHIH

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30
Q

Is GH present in large or small quantities? More in kids or adults?

A

Large in BOTH

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31
Q

Is the rate of secretion of GH/GHRH relatively constant or fluctuates?

A

It undergoes rapid spontaneous fluctuations as well as increasing/decreasing in response to specific stimuli

32
Q

What is the basal GH in plasma in children and adults?

A

0-3ng/ml

33
Q

Is this 0-3ng/ml an accurate number?

A

No since spikes of secretion occur every 24 hours or so

Meaning in children and puberty it is 5-8ng/ml and in adults it is 2-4 ng/ml

34
Q

When in children is GH secretion increased by 20x? Why is this?

A

Deep delta sleep since general energy requirements are low so energy redirected to growth

35
Q

What needs to be done in order to get a true picture of hormone status?

A

Repeated measurements over a period of time

36
Q

GH plasma levels spike…what about IGF-1?

A

These remain constant suggesting it buffers the pulsatile variance in GH levels

37
Q

Why is 50% of GH bound in blood even though it is a peptide hormone?

A

Helps provide a reservoir of GH in the blood which helps smooth out effects if the erratic secretions

38
Q

What is somatostatin’s secretion pattern like?

A

Tends to be “tonic” - slow and responsive to need

39
Q

Stimuli that increase GHRH = GH secretion?

A

Actual/potential decrease in energy supply to cells
Increased levels of amino acids in plasma
Stressful stimuli
Delta sleep
Oestrogen and androgens

40
Q

Why does a decrease in energy supply to cells increase GH levels?

A

GH needed for maintenance of tissues and their energy supply.

In hypoglycaemia there is a reduced substrate supply

In exercise and in the cold there is an increased demand for energy demand for energy.

All stimulate GH.

41
Q

Why does increase in AA increase GH?

A

GH promotes AA transport and protein synthesis

42
Q

Where is protein synthesised?

A

Muscle and liver

43
Q

Give examples of stressful stimuli that increase GH levels?

A

Infections

Psychological stress

44
Q

Why is an increase in GH during delta sleep useful for adults?

A

Repair of tissues

45
Q

What causes increase in somatostain/GHIH?

A

Glucose
FFAs
REM sleep
Cortisol

46
Q

What do subjects deprived of REM sleep show high levels of?

A

GH

47
Q

Why does cortisol affect GH activity?

A

It has an inhibitory effect on growth but mainly because it causes catabolism of proteins rather than releasing GHIH

48
Q

What 3 factors contribute to growth?

A

Hormones
Nutrition
Genes

49
Q

What hormones contribute to growth?

A 
GH
IGF-1
Insulin
Glucocorticoids
Thyroid hormone
Sex hormones (Androgens and Oestrogens)
50
Q

When are sex hormones influence on growth dominant?

A

After puberty

51
Q

Is GH and IGF-1 a major growth inducing hormone during the foetal stage?

A

No - mainly insulin and IGF-2

52
Q

What are thyroid hormones particularly important for?

A

Development of the NS in utero and early childhood

53
Q

What are thyroid hormones effects permissive to?

A

GH/IGF-1

54
Q

What affects do thyroid hormones have on the body?

A

Ossification of cartilage
Teeth maturation
Contours of face and proportions of the body

55
Q

What is cretinism?

A

A condition where children are hypothyroid from birth leading to retarded growth and infantile facial features

Known as hypothyroid dwarf

56
Q

Why does hypothyroidism cause retarded growth?

A

Loss of THs permissive effects on GH

57
Q

What levels of GH do hypothyroid dwarfs have?

A

Normal

58
Q

Do hypothyroid tadpoles eventual mature into frogs?

A

No chance man

59
Q

How does nutrition effect growth?

A

Need sufficient levels of protein and essential vit. and minerals as well as calories, especially in utero and development in childhood

60
Q

How does injury and disease stunt growth?

A

It leads to increased protein catabolism

61
Q

What do genetic factors do in regards to growth?

A

Helps determine max growth

62
Q

What are the 2 periods of rapid growth in humans?

A

Infancy

Puberty

63
Q

What happens in puberty to cause growth?

A

(sex hormones) Androgens and oestrogens produce spikes in GH which increases IGF-1 which promotes bone elongation for height and increases weight and mass

64
Q

What hormones terminate growth and how?

A

The same androgens and oestrogens that started it - by causing epiphyses of the long bones to fuse

65
Q

What causes hypersecretion of GH?

A

Gigantism

Acromegaly

66
Q

What causes excess GH in gigamtism ?

A

A pituitary tumour before the epiphyseal plates of long bones close - which is what leads to excessive growth

67
Q

What causes excess GH in Acromegaly?

A

Pit. tumour after epiphyseal plates close

68
Q

In acromegaly, what does excess GH lead to and why not height growth?

A

Epiphyseal plates are closed so no height increase

But bones grow in other directions = enlarged hands and feet

69
Q

What is a classic sign of acromegaly?

A

Feet should not get bigger in acromegaly

70
Q

Treatment for acromegaly?

A

Surgical removing of tumour

Somatostatin analogues

71
Q

Dwarfism may be due to?

A 
GHRH deficiency 
GH secreting cells are abnormal
Defective GH receptors 
Genetic mutations
Precocious puberty
Hypothyroid in children
72
Q

If there is a GHRH def. what can you do?

A

Administer GHRH and if you see positive results you found the cause

73
Q

If GH receptors are defective - why is GH conc. increased in body?

A

Defective GH receptor prevents IGF-1 release and peripheral tissues cannot respond to growth signal

Loss of IGF-1 inhibition feedback loop of GH leads to high levels of GH

74
Q

Give an example a type of culture with a genetic condition causing them to be short - what do these genes actually cause on a pathological level?

A

The pygmy people

Genetic mutation that impairs the ability of cells to produce IGF-I in response to GH

75
Q

Why does precocious puberty lead to stunted growth?

A

Excess gonadotropin releasing hormone (GnRH) releases sex hormones which fuse long bones early

76
Q

Why do hypothyroid children retain infantile features with stunted growth?

A

Due to loss of permissive effects TH has on GH

This limits bone growth, promotes fat storage and can severely impact neurological development

77
Q

Main difference between hypothyroid kids and kids deficient in GH?

A

Hypothyroid children retain infantile proportions

Children deficient in GH are proportionally normal, just small in height

ZA - Endocrine System (21 decks)

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