pituitary

Question 1

outcome of excess growth hormone in children

Answer 1

gigantism

Question 2

outcome of excess growth hormone in adults

Answer 2

acromegaly

Question 3

common cause of excess growth hormone

Answer 3

benign growth hormone secreting pituitary adenoma

Question 4

feature of gigantism

Answer 4

constant growing and early death as many metabolic effects

Question 5

feature of acromegaly signs and symptoms

Answer 5

insidious in onset (signs and symptoms progressing gradually)

Question 6

common causes of death if untreated excess GH in acromegaly

Answer 6

CVD (60%), respiratory complications (25%), cancer (15%) as huge daily excess of GH

Question 7

5 things that grow in acromegaly

Answer 7

soft tissue growth: periosteal bone, cartilage, fibrous tissue, connective tissue, internal organs (cardiomegaly, splenomegaly, hepatomegaly etc.)

Question 8

8 clinical features of acromegaly

Answer 8

hyperhidrosis (excessive sweating); headache; enlargement of supraorbital ridges, nose, hands and feet, thickening of lips and general coarseness of features; macroglossia (enlarged tongue); prognathism (mandible grows causing protrusion of lower jaw - dental problems); carpal tunnel syndrome (median nerve compression); barrel chest; kyphosis (rounding of upper back)

Question 9

how does excess growth hormone in acromegaly cause diabetes mellitus

Answer 9

excess growth hormone -> increased endogenous glucose production, decreased muscle glucose uptake -> increased insulin production causing increased insulin resistance -> impaired glucose tolerance -> diabetes mellitus

Question 10

4 complications of acromegaly

Answer 10

obstructive sleep apnoea, hypertension, cardiomyopathy, increased cancer risk

Question 11

how does acromegaly cause obstructive sleep apnoea

Answer 11

bone and soft-tissue changes surrounding upper airway lead to narrowing and subsequent collapse during sleep

Question 12

how does acromegaly cause hypertension

Answer 12

direct effects of GH and/or IGF1 on vascular tree; GH mediated renal Na+ reabsorption

Question 13

how does acromegaly cause cardiomyopathy (damage to heart muscle)

Answer 13

hypertension, diabetes mellitus, direct toxic effects of excess GH on myocardium

Question 14

how does acromegaly cause increased cancer risk, and what is done to mitigate risk

Answer 14

colonic polyps, so must have regular screening with colonoscopy

Question 15

what is co-secreted with growth hormone in acromegaly and why

Answer 15

prolactin, may reflect tumour secreting GH and prolactin

Question 16

following excess GH, and subsequent prolactin secretion in acromegaly, what may hyperprolactinaemia cause to gonads

Answer 16

secondary hypogonadism

Question 17

regulation of GH secretion

Answer 17

GHRH from hypothalamus stimulates GH secretion, somatostatin from hypothalamus inhibits GH secretion

Question 18

what is secreted when GH reaches liver

Answer 18

somatomedins (mainly IGF1)

Question 19

why is random GH measurement unhelpful in acromegaly diagnosis

Answer 19

GH is pulsatile

Question 20

2 tests used to diagnose acromegaly

Answer 20

elevated serum IGF1; oral glucose tolerance test (failed suppression (paradoxical rise) of GH following oral glucose load)

Question 21

glucose-induced suppression of GH secretion: normal

Answer 21

upon administering 75g oral glucose: GH starts at 2mU/l but will descend quickly before slowing to 0mU/l for an hour, then gradually rises after 2.5 hours to just over 3mU/l, before slowly decreasing and reaching normal after 4.5 hours

Question 22

glucose-induced suppression of GH secretion: acromegaly

Answer 22

upon administering 75g oral glucose: GH starts at 6 mU/l but will ascend quickly before slowing for an hour to 35 mU/l, then gradually decreases after 2 hours back to 6 mU/l

Question 23

4 treatments of acromegaly

Answer 23

trans-sphenoidal surgery up nose (first line) to remove tumour, somatostatin analogues (e.g. octreotide) to shrink tumour and reduce GH, dopamine agonists (e.g. cabergoline, as GH secreting pituitary tumours frequently express D2 receptors), radiotherapy

Question 24

what treatment is known as “endocrine cyanide”

Answer 24

somatostatin analogues

Question 25

when can somatostatin analogues be injected

Answer 25

subcutaneous is short acting; can have monthly depot

Question 26

GI side effects of somatostatin analogues

Answer 26

nausea, diarrhoea, gallstones, poor fat absorption

Question 27

desired therapeutic effect of somatostatin analogues

Answer 27

reduction in GH secretion and tumour size

Question 28

effect of somatostatin analogues pre-surgery

Answer 28

may make resection easier

Question 29

when would somatostatin analogues be used post-operatively

Answer 29

if surgery unsuccessful (not cured), or whilst waiting for radiotherapy to take effect (slow)