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*Diabetes & Endocrinology > Normal Growth and Clinical Aspects > Flashcards

Normal Growth and Clinical Aspects Flashcards

1
Q

If u can, name 7 factors by which growth is regulated?

A
  1. growth hormone release form AP
  2. thyroid hormones
  3. insulin
  4. sex steroids
  5. availability of nutrients
  6. stress
  7. genetics
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2
Q

What type of hormone is growth hormone?

A

Peptide

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3
Q

Where is growth hormone (GH) released from?

A

Anterior pituitary

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4
Q

What is another name for growth hormone?

A

Somatotrophin

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5
Q

GH release is controlled via the release of which 2 hypothalamic neurohormones with opposing action?

A

Growth Hormone Inhibiting Hormone (GHIH)

Growth Hormone Releasing Hormone (GHRH)

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6
Q

What is another name for GHIH?

A

Somatostatin (opposite of somatotrophin)

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7
Q

What are the 2 broad categories of the action of growth hormone?

A
  1. Growth and development (indirect)

2. Regulation of metabolism (direct)

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8
Q

At what age does GH become the dominant influence on the rate at which children grow?

A

After 8-10 months 9 (before this it is largely nutrition)

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9
Q

What does GH require the permissive action of in order to stimulate growth?

A

Thyroid hormones and insulin

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10
Q

Growth-promoting effect of GH is mediated through stimulation of what in cells of its target tissues?

A

Hypertrophy

Hyperplasia

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11
Q

How is GH action indirect?

A

It is acheived through action of an intermediate known as insulin-like growth factor (IGF-1)

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12
Q

What is IGF-1 also known as?

A

Somatomedin C (MEDIates action of GH)

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13
Q

Why is IGF-1 ‘insulin-like’?

A

Binds to receptors v similar to insulin (tyrosine) receptor

Has hypoglycaemic qualities

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14
Q

What is the limitation to the hypoglycaemic quality of IGF-1?

A

Limited to glucose uptake in muscle (liver + adipose have few IGF receptors)

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15
Q

What stimulates the secretion of IGF-1 from the liver?

A

GH release

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16
Q

How does IGF-1 then control the release of GH?

A

Negative feedback loop

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17
Q

(not important) does IGF-II exist? what is its function?

A

yes; limited to foetus + neonate

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18
Q

What type of hormones are GH and IGF-1? What type of hormones do they behave like transport-wise?

A

Peptide

Behave like steroid/thyroid hormones - transported in blood bound to carrier proteins

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19
Q

What percentage of GH is transported in bound form?

A

50%

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20
Q

What is the purpose of GH traveling bound to protein?

A

Provides ‘reservoir’ of GH - helps smooth out effects of erratic pattern of secretion and extends half life

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21
Q

How does IGF-1 exhibit neg feedback on GH release?

A

Via inhibition of GHRH and stimulation of GHIH

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22
Q

What is an additional neg feedback loop of GH?

A

on GH release from somatotrophs in pituitary

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23
Q

GIve the 3 effects of GH/IGF-1 on bone?

A
  1. GH stimulates chondrocyte precursor cells in epiphyseal plates to differentiate into chondrocytes
  2. During differentiation, the cells secrete IGF-I and become responsive to it
  3. IGF-1 then acts as an autocrine/paracrine agent to stimulate the differentiating chondrocytes to undergo cell division and produce cartilage, the foundation for bone growth
24
Q

When do epiphyseal plates close and what does this mean for growth?

A

Close during adolescence under influence of sex steroids, meaning no further longitudinal growth is possible

25
Q

Give 3 direct effects of GH (that can be descirbed as ‘anti-insulin’ effects)

A
  1. increases gluconeogenesis by the liver
  2. reduces the ability of insulin to stimulate glucose uptake by muscle and adipose tissue
  3. makes adipocytes more sensitive to lipolytic stimuli
26
Q

In these 3 actions, what is the general effect GH is having?

A

Releasing energy stores to support growth (of bone, heart, brain etc - rather than muscle + fat)

27
Q

Due to having this ‘anti-insulin’ effect, what hormone does is synergise with?

A

Cortisol

28
Q

Why is GH said to be diabetogenic?

A

It increases blood glucose when present in excess

29
Q

Give one direct effect of GH which is LIKE insulin, and unlike cortisol

A

Increases muscle, liver + adipose tissue amino acid uptake and protein synthesis = anabolic while cortisol is catabolic to protein (in this way GH also supports muscle growth)

30
Q

For growth what 2 hormones are needed?

A

Insulin and GH

31
Q

When in your lifetime are the highest rates of secretion of GH?

A

Teenage years

32
Q

Describe the secretion rate of GH

A

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

33
Q

What time of day are the highest rates of secretion of GH?

A

First 2 hrs of sleep (deep delta)

34
Q

Why is energy diverted to growth during sleep?

A

General energy requirements are low (vice versa during waking hours GH release is low)

35
Q

Nutritional control of GH release is mainly mediated via modulation of control of…

A

GNRH/GHIH release from hypothalamus

36
Q

Give 5 stimuli for GNRH secretion

A
  1. Actual/potential decrease in energy supply to cells
  2. Increased amino acids in plasma
  3. Stressful stimuli
  4. Delta sleep
  5. Oestrogen + testosterone
37
Q

Give a few examples of when there may be a decrease in actual/potential energy supply to cells

A

Fasting + hypoglycaemia (decrease in substrate supply)

Exercise + cold (increased demand for energy)

38
Q

Give an example of of stressful stimuli

A

Infection

Psychological stress

39
Q

Give 4 stimuli for GHIH (somatostatin) secretion

A
  1. Glucose
  2. FFA
  3. REM sleep
  4. Cortisol (although may be more to do with increased protein catabolism)
40
Q

The physiology of growth is a v complex phenomenon affected by which 3 factors?

A

HORMONES
NUTRITION
GENETICS

41
Q

Give the 7 hormones/types of hormones involved in growth

A 
GH
IGF-1
Thyroid hormones
Androgens
Oestrogens
Glucocorticoids
Insulin
42
Q

What are babies deficient in GH and IGF-1 born like?

A

They are of normal size (insulin and IGF-II are the hormones dominating intrauterine growth)

43
Q

What are thyroid hormones particularly important in?

A

Development of nervous system in utero and early childhood

44
Q

What do thyroid hormones have a permissive effect on?

A

GH/IGF-1

45
Q

What is cretinism?

A

Condition where children are hypothyroid from birth causing retarded growth from loss of TH’s permissive action on GH

46
Q

Why does injury and disease stunt growth?

A

Increased protein catabolism (glucocorticoid effects)

47
Q

What do genetic factors determine?

A

Maximum growth

48
Q

What are the 2 periods of rapid growth in humans?

A

Infancy

Puberty

49
Q

What is the nature of growth during infancy?

A

episodic

50
Q

What is the cause of growth during puberty?

A

Androgens and oestrogens

51
Q

What is the effect of these sex steroids in normal puberty?

A

Produce spikes in GH + IGF-1 secretion, promoting bone elongation and increased height, weight + body mass before they then terminate growth by causing closure of epipyseal plates

52
Q

Give 2 conditions which occur as a result is hypersecretion of GH

A

Gigantism

Acromegaly

53
Q

What is usually the cause of GH hypersecretion?

A

Endocrine tumours

54
Q

What is a characteristic of gigantism?

A

Pituitary tumour BEFORE epipyseal plates close so excessive long bone growth - patient can be more than 7ft tall

55
Q

What is a characteristic of acromegaly?

A

Pituitary tumour AFTER epiphyseal plates close so long bones cannot increase - can still grow in other directions tho so patient will have enlarged hands, jaw + feet

56
Q

How to treat acromegaly/gigantism?

A

Surgically remove tumour or somatostatin analogues

*Diabetes & Endocrinology (24 decks)

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