2. Hypersecretion of anterior pituitary hormones

Question 1

what can hypersecretion of the anterior pituitary be due to?

Answer 1

• isolated pituitary tumours

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

Question 2

what is hypersecretion of the anterior pituitary often associated with?

Answer 2

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

Question 3

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

Answer 3

absence of CSF

Question 4

what is bitemporal hemianopia?

Answer 4

tunnel vision

Question 5

what is bitemporal hemianopia caused by?

Answer 5

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

Question 6

what might compress fibres at the optic chiasm?

Answer 6

suprasella tumour

Question 7

how can visual fields be examined?

Answer 7

perimetry

Question 8

what does excess ACTH (corticotrophin) result in?

Answer 8

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

Question 9

what does excess TSH (thyrotrophin) result in?

Answer 9

thyrotoxicosis - high TSH and high T4

Question 10

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

Answer 10

early puberty in children

Question 11

what does excess prolactin result in?

Answer 11

hyperprolactinaemia

Question 12

what does excess GH result in?

Answer 12

gigantism (in children) and acromegaly (in adults)

Question 13

in which situations is it physiological to have high prolactin?

Answer 13

pregnancy and breastfeeding

Question 14

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

Answer 14

lactotroph hyperplasia

Question 15

what are the pathological causes of hyperprolactinaemia?

Answer 15

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

Question 16

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

Answer 16

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

Question 17

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

Answer 17

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

Question 18

how is prolactin secretion regulated?

Answer 18

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

Question 19

how can hyperprolactinaemia be treated?

Answer 19

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

Question 20

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

Answer 20

• more effective

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

Question 21

what are the side effects of dopamine receptor agonists?

Answer 21

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

Question 22

what is gigantism and what are its effects?

Answer 22

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

Question 23

what is acromegaly and what are its effects?

Answer 23

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)

Question 24

what grows in acromegaly?

Answer 24

• periosteal bone
• cartilage
• fibrous tissue
• connective tissue
• internal organs

Question 25

what are the clinical features of acromegaly?

Answer 25

• 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

Question 26

what are the metabolic effects of acromegaly?

Answer 26

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

Question 27

what are complications of acromegaly?

Answer 27

• 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

Question 28

how can acromegaly be diagnosed?

Answer 28

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

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

Question 29

what are the treatments of acromegaly?

Answer 29

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

Question 30

how are somatostatin analogues used to treat acromegaly?

Answer 30

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

Question 31

when may somatostatin analogues be used?

Answer 31

pre-treatment: to make surgery easier

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

Question 32

what are the common GI side effects of somatostatin analogues?

Answer 32

nausea, diarrhoea, gallstones

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