2. Hypersecretion of anterior pituitary hormones Flashcards

1
Q

what can hypersecretion of the anterior pituitary be due to?

A
  • isolated pituitary tumours

- can also be ectopic (from non-endocrine tissue e.g. neuroendocrine tumours)

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2
Q

what is hypersecretion of the anterior pituitary often associated with?

A

often associated with visual field and other defects (e.g. cranial nerves)

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3
Q

what does an absence of black in an MRI scan mean?

A

absence of CSF

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4
Q

what is bitemporal hemianopia?

A

tunnel vision

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5
Q

what is bitemporal hemianopia caused by?

A

compression of the fibres from the nasal retinae that cross at the optic chiasm, leading to loss of vision from the outer temporal visual fields

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6
Q

what might compress fibres at the optic chiasm?

A

suprasella tumour

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7
Q

how can visual fields be examined?

A

perimetry

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8
Q

what does excess ACTH (corticotrophin) result in?

A

cushing’s disease (if due to anterior pituitary tumour)

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9
Q

what does excess TSH (thyrotrophin) result in?

A

thyrotoxicosis - high TSH and high T4

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10
Q

what does excess gonadotrophins (LH,FSH) result in?

A

early puberty in children

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11
Q

what does excess prolactin result in?

A

hyperprolactinaemia

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12
Q

what does excess GH result in?

A

gigantism (in children) and acromegaly (in adults)

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13
Q

in which situations is it physiological to have high prolactin?

A

pregnancy and breastfeeding

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14
Q

what do you get at the end of pregnancy to prepare for breastfeeding?

A

lactotroph hyperplasia

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15
Q

what are the pathological causes of hyperprolactinaemia?

A

prolactinoma (often a microadenoma so <10mm in diameter)

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16
Q

what effect does high prolactin have on LH and FSH production?

A

suppresses GnRH pulsatility -> less GnRH -> less LH and FSH production

17
Q

what does hyperprolactinaemia due to prolactinoma cause in women and men?

A

women: glactorrhoea (milk production), secondary amenorrhoea (or oligomenorrhoea) due to decreased LH and FSH, loss of libido, infertility
men: loss of libido, erectile dysfunction, infertility

18
Q

how is prolactin secretion regulated?

A

dopamine released from hypothalamic dopaminergic neurones bind to D2 receptors all over the lactotroph to inhibit prolactin

19
Q

how can hyperprolactinaemia be treated?

A
  • dopamine receptor (D2) agonist (tablets) e.g. cabergoline and bromocriptine
  • tumour may need to be surgically removed if it is large
20
Q

why is cabergoline preferred over bromocriptine as a dopamine receptor agonist?

A
  • more effective

- needs to be taken 1/2 times a week rather than daily

21
Q

what are the side effects of dopamine receptor agonists?

A
  • nausea and vomiting
  • postural hypotension (dizziness)
  • dyskinesia
  • depression/anxiety
  • pathological gambling
22
Q

what is gigantism and what are its effects?

A

XS GH in children -> growth doesn’t stop and you keep on growing linearly

people with gigantism can die from infection because too much GH is not good for you

23
Q

what is acromegaly and what are its effects?

A

XS GH in adults -> increase in soft tissue growth and cartilage growth

can result in cardiovascular disease (predisposition to higher BP, glucose intolerance and diabetes), respiratory complications (soft tissue grows around neck/palate) and cancer (lots of GH causes malignancy)

24
Q

what grows in acromegaly?

A
  • periosteal bone
  • cartilage
  • fibrous tissue
  • connective tissue
  • internal organs
25
Q

what are the clinical features of acromegaly?

A
  • excessive sweating
  • headache
  • enlargement of supraorbital ridges, nose, hands and feet
  • thickening of lips and coarseness of features
  • enlarged tongue (macroglossia)
  • protrusion of lower jaw
  • carpal tunnel syndrome (median nerve compression due to tissue growth in wrist)
  • barrel chest
26
Q

what are the metabolic effects of acromegaly?

A

excess GH -> increased glucose production -> decreased muscle glucose uptake -> increased insulin production -> increased insulin resistance -> impaired glucose tolerance -> diabetes

27
Q

what are complications of acromegaly?

A
  • obstructive sleep apnoea: narrowing of upper airway and possible collapse due to tissue growth
  • hypertension: GH/IGF-1 effects directly, GH mediated renal sodium reabsorption
  • cardiomyopathy: hypertension, DM
  • increased risk of cancer: colonic polyps
28
Q

how can acromegaly be diagnosed?

A

IGF-1 is not pulsatile so elevated IGF-1 serum

oral glucose test: paradoxical risk of GH following oral glucose load

29
Q

what are the treatments of acromegaly?

A
  1. surgery to remove tumour
  2. somatostatin analogues (e.g. octreotide) and dopamine agonists (e.g. cabergoline)
  3. radiotherapy
30
Q

how are somatostatin analogues used to treat acromegaly?

A

short lasting injection/monthly depot which reduce GH secretion dramatically and shrink the tumour

31
Q

when may somatostatin analogues be used?

A

pre-treatment: to make surgery easier

post-operatively: if not cured or waiting for radiotherapy to take effect

32
Q

what are the common GI side effects of somatostatin analogues?

A

nausea, diarrhoea, gallstones

this is because it is an ‘endocrine cyanide’ which inhibits lots of peptides, not just GH