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Diabetes & Endocrinology > Normal growth and clinical aspects > Flashcards

Normal growth and clinical aspects Flashcards

1
Q

Where is GH released from and what is its main action?

A

anterior pituitary

promote growth

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2
Q

What is another name for GH?

A

somatotrophin

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3
Q

What is meant by GH being species specific?

A

only human GH can be used in GHD
used to use GH direct from human pituitary
due to CJD infection now use recombinant

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4
Q

What 2 hormones have a permissive effect to GH and hence are essential for normal growth?

A

insulin

thyroid hormone

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5
Q

What type of hormone is GH but what is the exception to the normal rule of this class of hormones?

A

peptide

about 50% circulates bound to carrier proteins

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6
Q

Role of GH in adults

A

maintenance of tissues and their energy supply

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7
Q

When does GH take over as the main influence on growth and what predominates before this?

A

8-10 months

nutritional intake

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8
Q

Hyperplasia

A

increased cell division

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9
Q

hypertrophy

A

increased cell size

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10
Q

Is GH effect on growth direct or indirect?

A

indirect

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11
Q

What is the name of the intermediate which allows growth?

A

IGF1

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12
Q

What is another name for IGF-1?

A

somatomedin

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13
Q

What is IGF-1 structure similar to?

A

proinsulin

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14
Q

Name 3 ways IGF-1 is insulin like

A

hypoglycaemic qualities
similar structure to proinsulin
binds to receptors similar to insulin receptor

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15
Q

Where is IGF-1’s hypoglycaemic qualities limited to and why?

A

muscle

liver and adipose tissue have few IGF-1 receptors

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16
Q

Where is IGF-1 released from and in response to what?

A

LIVER and other tissues eg bone

increased GH from anterior pituitary

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17
Q

How does IGF-1 control GH

A

negative feedback loop

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18
Q

What is IGF-2 role?

A

limited to foetus and neonatal

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19
Q

Explain the IGF-1 and GH negative feedback loop

A

IGF-1 inhibits GHRH and stimulates GHIH

GH on GH release from somatotrophs in pituitary eg self regulation

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20
Q

What does GH do to prechondrocytes in the epiphyseal plate?

A

stimulate them to become chondrocytes

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21
Q

What do these chondrocytes secrete and what is the consequence of this

A

IGF-1

become IGF-1 responsive

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22
Q

Does IGF-1 act as autocrine/paracrine/endocrine in bone growth?

A

autocrine and paracrine

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23
Q

What happens In bone growth once IGF-1 is released and then bone is now IGF-1 sensitive?

A

chondrocytes undergo cell division and produce cartilage which is the foundation for bone growth

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24
Q

Why does the epiphyseal plate close and what is the consequence of this?

A

puberty/adolescence due to sex hormones

no more longitudinal bone growth

25
Q

What are the direct effects of GH?

A

increase gluconeogenesis by liver
reduce ability of insulin to stimulate glucose uptake by muscle/adipose
adipocytes more sensitive to lipolytic stimuli
release energy stores to support growth

26
Q

Is GH said to be anti or pro insulin?

A

anti

27
Q

How is 1 way that GH is like insulin and not like cortisol

A

increase muscle, liver and adipose tissue amino acid uptake and protein synthesis –> anabolic

28
Q

Where are GHRH and GHIH secreted from?

A

hypothalamus

29
Q

Explain the differences in the basal plasma and 24 hour mean rates of GH in children and adults

A

basal GH - same

24 hour mean - children higher due to spikes of secretion

30
Q

What phase of sleep is GH highest and why?

A

deep delta sleep

general energy requirement low and energy diverted to growth

31
Q

Why must repeated hormone measurements be taken?

A

to get a true picture of hormone status due to spikes

32
Q

Does IGF-1 have spikes or constant? Result of this?

A

constant

buffers pulsatile variance in GH levels

33
Q

Advantage of 50% of GH bound to carrier proteins

A

reservoir of GH

smooths out effects of erratic pattern of secretion

34
Q

How would you describe GHIH secretion?

A

tonic

slow and responsive to needs

35
Q

5 things that increase GHRH secretion and hence increase GH

A 
actual or potential decrease in energy supply 
increased amino acids in plasma 
delta sleep 
stressful stimuli eg infection, stress
oestrogen and androgens
36
Q

Why does an actual or potential decrease in energy stimulate GHRH secretion?

A

GH needed for maintenance of tissue and energy supply
in fasting/hypoglycaemia decreased substrate supply
exercise and cold increase energy demand
all stimulate increase in GH

37
Q

Why does increased amino acids in plasma increase GH?

A

protein meal

GH promotes amino acid transport and protein synthesis by muscle and liver

38
Q

4 stimuli which increase GHIH secretion and hence decrease GH

A

cortisol
glucose
FFA
REM sleep

39
Q

Why is cortisol inhibitory on growth?

A

promotes GHIH

increase protein catabolism

40
Q

3 important factors in the physiology of growth

A

hormones
nutrition
genetics

41
Q

Name some hormones important in growth

A

thyroid hormone, insulin, GH, IGF1, oestrogen, cortisol, androgens

42
Q

When do sex hormones start playing a major role in growth?

A

puberty

43
Q

What is TH important for in growth?

A

permissive to IGF-1 and GH
nervous system development in utero and childhood
ossification of cartilage and teeth maturation
contours of face

44
Q

What is cretinism?

A

hypothyroid - infant facial features
decreased growth
hypothyroid dwarf

45
Q

Why do injury and disease stunt growth?

A

increased catabolism

glucocorticoid effects

46
Q

what are the 2 periods of rapid growth

A

infancy

puberty

47
Q

Explain infancy rapid growth

A

can grow 2.5cm in a few days then nothing

EPISODIC

48
Q

Explain puberty rapid growth

A

androgens and oestrogens
spikes in GH and IGF-1
same hormones terminate growth

49
Q

What hormones influence bone elongation before the epiphyseal plates fuse?

A

GH and IGF-1

50
Q

What hormones cause the epiphyseal plates to fuse?

A

sex hormones

51
Q

What is usually the cause of hypersecretion of GH?

A

endocrine tumours

52
Q

Cause of gigantism

A

excess GH before epiphyseal plates fuse

53
Q

Cause of acromegaly

A

excess GH after epiphyseal plates fuse

54
Q

What happens in acromegaly?

A

cannot increase longitudinal bone growth

grow in other directions eg hands and feet

55
Q

What is adults feet increasing in size a sign of?

A

acromegaly

56
Q

Treatment for acromegaly

A

remove tumour

GHIH analogues

57
Q

List some reasons for reduced growth

A 
precocious puberty 
genetic mutations 
deficient in GHRH 
GH secreting cells abnormal 
end organ unresponsive to GH
hypothyroid children
58
Q

How do children deficient in GH or TH differ in proportions?

A

both small
hypothyroid - infant proportions
GH - small but normal proportions

Diabetes & Endocrinology (24 decks)

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