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Year 2 - Endocrine > Normal growth + clinical aspects > Flashcards

Normal growth + clinical aspects Flashcards

1
Q

Growth is regulated by what different factors (7)

A 
Growth hormone (from AP)
Thyroid hormones
Insulin
Sex steroids (mainly at puberty)
Nutrient availability
Stress
Genetics
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2
Q

Growth hormone release is regulated by the balance of what 2 other hormones from the hypothalamus

A

GHRH

GHIH aka somatostatin

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3
Q

Growth hormone aka

+ secreted by

A

somatotropin

AP

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4
Q

Growth hormone has a DIRECT and INDIRECT action

  • what does the indirect action do
  • what does the direct action do
A

Indirect action - involved in growth and development

Direct action - regulates metabolism

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5
Q

Growth in the foetal period and 10 months of life is largely dependent on what

A

nutritional intake (NOT GROWTH HORMONE)

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6
Q

After what age does growth hormone become the dominant influence of growth

A

After 10 months

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7
Q

GH requires the PERMISSIVE action of what other things before it can stimulate growth, without these GH itself stunts growth

A

Thyroid hormones

Insulin

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8
Q

GH secretion continues throughout adult life - why?

A

essential in maintenance and repair of tissue

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9
Q

How does GH stimulate growth (2)

A

Stimulates hypertrophy + hyperplasia (cell division) in its target tissues

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10
Q

Growth hormone has a DIRECT and INDIRECT action:

Indirect action:

Describe how GH indirectly promotes growth + development (3)
-mention what intermediate is involved

A

Involves the intermediate, insulin-like growth factor-1 (IGF-1) aka somatomedin C

GH stimulates chondrocyte precursor cells in epiphyseal plates to differentiate into chondrocytes

During differentiation, the chondrocytes begin to secrete IGF-1 and become responsive to IGF-1

IGF-1 then acts as an autocrine/paracrine agent to stimulate the differentiating chondrocytes to undergo cell division + produce cartilage –> calcifies into bone

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11
Q

Insulin-like growth factor-1 (IGF-1) has a structure similar to what + what tissue does it have most effect on

A

Pro-insulin

Mostly causes glucose uptake in muscle as liver and adipose tissue have few IGF receptors

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12
Q

IGF-1 is secreted by what organ in response to GH release

A

Liver

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13
Q

How does IGF-1 control GH release

A

Via a negative feedback loop

-presence of IGF-1 feedbacks to the hypothalamus to inhibit GHRH and stimulate GHIH

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14
Q

Does GH travel freely in the blood

A

50% is bound to protein to provide a reservoir of GH

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15
Q

Somatostatin aka

+ secreted by

A

GHIH

hypothalamus

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16
Q

Somatomedin C aka

A

Insulin-like growth factor-1 (IGF-1)

-mediates GH

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17
Q

Apart from IGF-1 exhibiting negative feedback on GH release, what else exhibits negative feedback on GH release

A

GH itself has a negative feedback loop on its own release from somatotropin in the pituitary gland

18
Q

What stimulates epiphyseal plates to close during adolescence (i.e. no further longitudinal growth)

A

Sex steroids - stimulate apoptosis of chondrocytes

19
Q

Growth hormone has a DIRECT and INDIRECT action:

DIRECT action:

Describe 4 mechanisms that GH DIRECTLY regulates metabolism

A
  1. Increases gluconeogenesis by the liver.
  2. Reduces the ability of insulin to stimulate glucose uptake by muscle and adipose tissue.
  3. Promotes lipolysis to provide additional energy
  4. Increases amino acid uptake and protein synthesis in almost all cells = ANABOLIC effect
20
Q

Growth hormone DIRECTLY regulates metabolism via 4 mechanisms:

  1. Increases gluconeogenesis by the liver.
  2. Reduces the ability of insulin to stimulate glucose uptake by muscle and adipose tissue.
  3. Promotes lipolysis to provide energy source
  4. Increases amino acid uptake and protein synthesis in almost all cells = ANABOLIC effect

What is common about the first 3 mechanisms?

What’s different about the 4th mechanism?

A

In all of these actions GH is releasing energy stores to support growth.

It is having an “anti-insulin” effect and synergises with CORTISOL in this respect.

GH is therefore said to be diabetogenic (increases blood glucose) when present in excess

4th mechanism - GH acts unlike cortisol and just like insulin

21
Q

Are insulin and GH catabolic or anabolic hormones

A

anabolic

22
Q

What does insulin stimulate that GH doesn’t

A

glucose uptake

23
Q

Highest rates of secretion of GH occur during what years of life

A

teen

24
Q

Secretion rate of GH undergoes rapid spontaneous fluctuations over 24 hours, however plasma levels of IGF-1 remain quite constant which suggests what

A

IGF-1 buffers the pulsatile variance in GH levels

25
Q

As well as IGF-1 and GH itself controlling the release of GH, what else is GH secretion influenced by

A

Nutritional status

-mediates GH release via control of GHRH/GHIH release from hypothalamus

26
Q

Stimuli that increase GHRH secretion (therefore increasing GH secretion)

A
  1. Decrease in energy supply to cells
  2. Increased plasma amino acids
  3. Stressful stimuli, e.g. infection, psychological stress
  4. Delta sleep
  5. Oestrogen and testosterone
27
Q

How does decreased energy supply to cells stimulate GHRH secretion thus increasing GH secretion

A

GH is also needed for maintenance of tissues and their energy supply, so in situations where more energy is needed like fasting, exercise, cold weather, energy demand is increased which stimulates GH secretion

28
Q

How does a rise in the plasma amino acid level after the digestion and absorption of a large protein meal affect GH secretion

A

Would stimulate an increase in GHRH secretion thus increasing GH secretion as GH promotes amino acid transport and protein synthesis by muscle and lover

29
Q

Stimuli that increase GHIH secretion (thus decreasing GH secretion) (4)

A

Glucose
Free fatty acids
REM sleep
Cortisol

30
Q

3 factors affecting growth

A

Hormones
Nutrition
Genetics

31
Q

Name 6 hormones that affect growth

A 
GH
Insulin-like growth factor-1 (IGF-1)
Thyroid hormones
Sex steroids
Glucocorticoids
Insulin
32
Q

What 2 hormones are associated with intrauterine growth

A

Insulin

IGF-II

33
Q

What stages of life are thyroid hormones particularly important (2)

A

In utero - for development of nervous system

Early childhood

34
Q

What is cretinism

A

Condition where children are hypothyroid from birth.

They have retarded growth because of the loss of thyroid hormone’s permissive action on GH

GH LEVELS ARE NORMAL

35
Q

2 periods of rapid growth occur in humans - when are they

A

Infancy

Puberty

36
Q

Hypersecretion of GH is usually due to what pathology

A

Endocrine tumours

37
Q

What is gigantism

A

Excess GH due to a pituitary tumour BEFORE epiphyseal plates of long bones close –> excessive growth

38
Q

What is acromegaly

A

Excess GH due to a pituitary tumour AFTER epiphyseal plates have sealed.

Long bones cannot increase so there is no longitudinal growth and no increase in height but non-long bones can still grow so can get big hands and feet

39
Q

Classic sign of acromegaly

A

Large feet

40
Q

Treatment of acromegaly (2)

A

Removal of tumour or somatostatin analogue

41
Q

Features of hypothyroid children v GH deficient children

A

Hypothyroid - retain infantile proportions (i.e. still look like an infant)

GH deficient - proportionally normal, just small/short

Year 2 - Endocrine (21 decks)

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