pituitary Flashcards
acromegaly and gigantism: recall the signs and symptoms of growth hormone hypersecretion in adults and children, recall principles of diagnosis, and recall treatment options
outcome of excess growth hormone in children
gigantism
outcome of excess growth hormone in adults
acromegaly
common cause of excess growth hormone
benign growth hormone secreting pituitary adenoma
feature of gigantism
constant growing and early death as many metabolic effects
feature of acromegaly signs and symptoms
insidious in onset (signs and symptoms progressing gradually)
common causes of death if untreated excess GH in acromegaly
CVD (60%), respiratory complications (25%), cancer (15%) as huge daily excess of GH
5 things that grow in acromegaly
soft tissue growth: periosteal bone, cartilage, fibrous tissue, connective tissue, internal organs (cardiomegaly, splenomegaly, hepatomegaly etc.)
8 clinical features of acromegaly
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)
how does excess growth hormone in acromegaly cause diabetes mellitus
excess growth hormone -> increased endogenous glucose production, decreased muscle glucose uptake -> increased insulin production causing increased insulin resistance -> impaired glucose tolerance -> diabetes mellitus
4 complications of acromegaly
obstructive sleep apnoea, hypertension, cardiomyopathy, increased cancer risk
how does acromegaly cause obstructive sleep apnoea
bone and soft-tissue changes surrounding upper airway lead to narrowing and subsequent collapse during sleep
how does acromegaly cause hypertension
direct effects of GH and/or IGF1 on vascular tree; GH mediated renal Na+ reabsorption
how does acromegaly cause cardiomyopathy (damage to heart muscle)
hypertension, diabetes mellitus, direct toxic effects of excess GH on myocardium
how does acromegaly cause increased cancer risk, and what is done to mitigate risk
colonic polyps, so must have regular screening with colonoscopy
what is co-secreted with growth hormone in acromegaly and why
prolactin, may reflect tumour secreting GH and prolactin
following excess GH, and subsequent prolactin secretion in acromegaly, what may hyperprolactinaemia cause to gonads
secondary hypogonadism
regulation of GH secretion
GHRH from hypothalamus stimulates GH secretion, somatostatin from hypothalamus inhibits GH secretion
what is secreted when GH reaches liver
somatomedins (mainly IGF1)
why is random GH measurement unhelpful in acromegaly diagnosis
GH is pulsatile
2 tests used to diagnose acromegaly
elevated serum IGF1; oral glucose tolerance test (failed suppression (paradoxical rise) of GH following oral glucose load)
glucose-induced suppression of GH secretion: normal
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
glucose-induced suppression of GH secretion: acromegaly
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
4 treatments of acromegaly
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
what treatment is known as “endocrine cyanide”
somatostatin analogues
when can somatostatin analogues be injected
subcutaneous is short acting; can have monthly depot
GI side effects of somatostatin analogues
nausea, diarrhoea, gallstones, poor fat absorption
desired therapeutic effect of somatostatin analogues
reduction in GH secretion and tumour size
effect of somatostatin analogues pre-surgery
may make resection easier
when would somatostatin analogues be used post-operatively
if surgery unsuccessful (not cured), or whilst waiting for radiotherapy to take effect (slow)
