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Pituitary tumour EAR:1 > Integrated endocrine physiology > Flashcards

Integrated endocrine physiology Flashcards

1
Q

what is lipolysis

  • What is it inhibited by
  • What is it stimulated by
A

Fat turned into FFA + glycerol

  • INhibted by insulin
  • Stimulated by glucagon, cortisol, GH and catecholamines
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2
Q

What is synergistic activity

A

Produce much greater enhanced response than sum of either of hormones alone

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3
Q

What is permissive activity

A

Presence of one hormone allows a second hormone to act

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4
Q

Where are growth hormones synthesised

A

Somatotrophs in anterior pituitary

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5
Q

What are the roles of the growth hormone

Where do they act

A

Growth and metabolism

Act via GH receptor on target cells

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6
Q

Action of growth hormone on metabolism (direct)

A

Liver- increased gluconeogenesis

Muscle- increased amino acid uptake, increased protein synthesis, decreased glucose uptake

Adipose tissue- increased lipolysis, decreased glucose uptake

overall effect- increased blood glucose

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7
Q

What is growth hormone synergistic with

A

Cortisol

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8
Q

What is the indirect effect of growth hormone

A

Promotes growth by stimulating release of growth factors such as IGF-1 (insulin-like growth factor) and IGF2 (somatomedins) from liver and other cell types

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9
Q

How does growth occur

A

Via the action of IGF1 on cells
-Stimulate protein synthesis, increase cell size (hypertrophy)

  • Stimulate cell division, increase cell number (hyperplasia)
  • Promote skeletal growth
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10
Q

What does the action of growth hormone on growth require

A

Presence of thyroid hormones (has a permissive role)

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11
Q

What role does thyroid hormone have

A

Permissive role on GH activity in promoting growth

Key role in CNS development

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12
Q

Other hormones important for growth and their roles

A

INsulin- important growth promoter. Also important intra-uterine growth factor

Sex hormones- dramatic rise during puberty. Linear growth, muscle building and stop bone elongation. by promoting epiphyseal plate closure

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13
Q

How do these affect bone growth and bone maturation:

  • Growth hormone
  • Thyroid hormone
  • Androgens
  • Oestrogens
  • Glucocorticoids
A

GH- bigger increase in liner growth than the increase in bone maturation

Thyroid- Increase in linear growth and maturation

Androgens and oestrogens- Increase in linear growth but bigger effect on bone maturation

Glucocorticoids- Decrease in linear growth and increase in bone maturation

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14
Q

What trophic effect do these anterior pituitary hormones have:

  • Prolactin
  • LH, FSH (gonadotropins)
  • TSH (thyrotropin)
  • ACTH (corticotropin)
A

Prolactin- breast
LH, FSH- testes, ovaries
TSH- Thyroid
-ACTH- adrenal cortex

Low levels of these cause atrophy

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15
Q

How does growth hormone have an effect on growth

A

Acts on liver and other tissues and via somatomedins has an indirect effect on growth

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16
Q

How is the release of GH controlled

A

Hypothalamus releases growth hormone releasing hormone which increases action of anterior pituitary which increases growth hormone release

Hypothalamus releases somatostatin which decreases action of anterior pituitary

17
Q

How does a decrease in blood glucose, decrease in FFA and increase in AA conc affect GH release

A

They increase the action of hypothalamus which releases more GHRH which acts on anterior pituitary and so more GH released.

This means there is increased gluconeogeneiss, increased lipolysis and increased amino acid uptake and protein synthesis which helps to increase blood glucose

18
Q

What effect do stress, sleep and exercise have on growth hormone secretion

A

Increase growth hormone secretion.

19
Q

What is the release of GH like during the day

A

Intermittent peaks throughout the day but 70% of the release is during sleep

20
Q

What does cortisol (glucocorticoid) have a synergistic effect with and what do they do

A

GH

Mobilise reserves and increase availability of glucose (esp. prolonged hypoglycaemia)

21
Q

What effect do chronic high glucocorticoid concentrations have and when might this be the case

A

Inhibit GH release (such as Cushing’s syndrome, long term use of high doses of steroids)

22
Q

What can stunted growth be because of

A

Pituitary dwarfism (GH deficiency)

Hypothyroidism

Cushing’s syndrome

CAH (congenital adrenal hyperplasia)

Sexual precocity

23
Q

What is used to treat growth hormone deficiency

A

Recombinant HGH (human growth hormone)

24
Q

Growth hormone deficiency symptoms

A
  • Psychological changes
  • MAlaise, excessive tiredness, anxiety and depression
  • Ostoporosis
  • Poor muscular tone, decrease in lean body mass
  • Impaired hair growth
  • Increase in adipose tissue especially around the waist
25
Q

How does Cushing’s lead to stunted growth

A

Excess cortisol inhibits GH release

Inhibits linear bone growth

26
Q

What is sexual precocity

A

Entering puberty before
f-age 8
m-age 9

27
Q

How do CAH and sexual precocity cause stunted growth

A

Increased androgens result in early/rapid bone maturation

28
Q

What can cause accelerated growth (tall stature)

A

Gigantism
Hyperthyroidism
Sexual precocity
Eunuchoidism

29
Q

How does gigantism cause accelerated growth

A

Tumour with GH excess

30
Q

How does hyperthyroidism cause accelerated growth

A

Excess thyroid hormones promote GH

31
Q

Difference between acromegaly and gigantism

A

Gigantism - excess GH in childhood

Acromegaly- excess GH in adulthood

32
Q

Symptoms of acromegaly

A 
Coarsening of facial features
Enlarged hands and feet 
Headaches, vision disturbance
Sleep apnoea, general tiredness
Hypertension, cardiomegaly
Glucose intolerance (diabetes)
Irregular or loss of periods (females); impotence in males
33
Q

How does sexual precocity cause accelerated growth

A

Initial accelerated bone growth (early growth spurt)

34
Q

How does eunuchoidism cause accelerated growth

A

Low sex hormone levels result in extension of long bone growth (delayed bone maturation)

Pituitary tumour EAR:1 (10 decks)

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