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MEH > 8. HPA & GH > Flashcards

8. HPA & GH Flashcards

1
Q

What is the embryological origin of the posterior pituitary?

A

Neuroectoderm - primitive brain tissue

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2
Q

What is the embryological origin of the anterior pituitary?

A

Oral ectoderm - primitive gut tissue

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3
Q

Which bone does the pituitary gland sit within?

A

Sella turcica

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4
Q

Which hormones are produced from the posterior pituitary?

A

ADH and oxytocin

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5
Q

Which hypothalamic nuclei produce ADH and oxytocin?

A

Supraoptic and paraventricular nuclei

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6
Q

Hormones synthesised in the hypothalamus are stored in the ______ ________ before release into the hypophyseal portal system.

A

Median eminence

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7
Q

What type of hormones are released from the hypothalamus to the anterior pituitary?

A

Tropic hormones - stimulate (or inhibit) endocrine cells in the anterior pituitary

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8
Q

What are the 6 tropic hormones produced by the hypothalamus?

A 
TRH
PIH
CRH
GnRH
GHRH
GHIH (somatostatin)
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9
Q

Why is the control of prolactin secretion unusual?

A

It is mainly inhibitory by PIH

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10
Q

What is PIH?

A

Dopamine

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11
Q

What are the 6 hormones produced by the anterior pituitary in response to the tropic hormones?

A 
TSH
PRL
ACTH
LH
FSH
GH
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12
Q

Which tropic hormones control the release of growth hormone from the anterior pituitary?

A

GHRH

GHIH (somatostatin)

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13
Q

What type of hormone is GH?

A

Protein

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14
Q

How are does GH exert most of it’s effect indirectly?

A

GH stimulates skeletal muscle and liver to produce IGF’s 1 and 2.

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15
Q

What is a major role of GH in childhood and teenage years?

A

Stimulates long bone growth, once epiphyseal plate closes, stimulates width growth.

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16
Q

What effect do IGF’s have on bone?

A

Stimulate bone and cartilage growth

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17
Q

What role does GH and IGFs have in adults?

A

Maintain muscle and bone mass
Promote healing and tissue repair
Modulate metabolism and body composition

18
Q

How does sleep influence GH secretion?

A

Surge in GH after onset of deep sleep

REM sleep decreases GH secretion.

19
Q

What conditions cause a rise in GH secretion?

A

Stress (trauma, fever)
Exercise
Fasting
Decrease in levels of glucose and FA

20
Q

What conditions cause a decrease in GH secretion?

A

Obesity

Increase in levels of glucose or fatty acid

21
Q

How is GH secretion regulated by long loop negative feedback?

A

Mediated by IGFs:

  • Inhibit release of GHRH and stimulate release of somatostatin from hypothalamus.
  • Inhibit release of GH from anterior pituitary
22
Q

How is GH secretion regulated by short loop negative feedback?

A

GH itself stimulates somatostatin release

23
Q

What is the condition caused by GH deficiency in childhood?

A

Pituitary dwarfism -proportionate

24
Q

How can pituitary dwarfism be treated?

A

GH therapy

25
Q

What is the condition caused by GH excess in children?

A

Gigantism

26
Q

What is the condition caused by GH excess in adults?

A

Acromegaly

27
Q

What are the signs of acromegaly?

A

Large extremities - hands, feet, lower jaw

28
Q

What is the most common cause of GH excess?

A

Pituitary adenoma

29
Q

How does GH exert its effect on cells?

A

Tyrosine receptor JAK kinases

30
Q

What happens when GH binds to it’s tyrosine kinase receptor?

A

Cross phosphorylation of JAK, phosphorylation of receptor and activation of pathways leading to transcription of IGF.

31
Q

Which IGF is mainly utilised for foetal growth?

A

IGF 2

32
Q

What response does IGF binding to target cells generate?

A

Cell growth (hypertrophy)
Cell number (hyperplasia)
Increase rate of protein synthesis
Increase lipolysis

33
Q

How do the actions of IGF and insulin differ?

A

Insulins effects are mainly metabolic
IGF mainly mitogenic
There is some cross-activation across receptors, especially at hybrid receptor.

34
Q

What is the hybrid receptor comprised of?

A

one subunit from the insulin receptor and one subunit from the IGF1 receptor, so binds to both insulin and IGF1.

35
Q

Which disease results from excess growth hormone secretion occuring after puberty after the epiphyseal plates have closed?

A

Acromegaly

36
Q

Why might a patient with a pituitary adenoma develop visual field loss?

A

The pituitary is in close proximity to the optic chiasm so growth of the adenoma can compress the optic nerves

37
Q

Which of the following is a symptom of hyperprolactinaemia in women?

A

Galactorrhoea - milky secretion from breasts

38
Q

Which biochemical finding would you expect in a patient with acromegaly?

A

Plasma IGF-1 above the normal range

39
Q

What is diabetes insipidus caused by?

A

Lack of ADH (vasopressin)

40
Q

What is a typical clinical consequence of untreated diabetes insipidus?

A

Hypernatraemia

41
Q

What is the pattern of cortisol concentration?

A

Cortisol is at its highest level in the morning and lowest level at midnight.

42
Q

Which type of drug can be used to treat prolactinoma?

A

Dopamine receptor agonist

MEH (19 decks)

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