Growth Hormone Flashcards
GH secretion
Secreted by somatotrophs
Most abundant hormone of adult anterior pituitary
GH release
Stimulated by sleep, exercise, stress
Inhibited by food ingestion
GH Hypothalamic influence
GHRH (positive)
Somatostatin (negative)
Random GH measurements
Little value
Pulsatile release
Short half life
GH stimulates production of
Insulin like growth factor 1 (IGF-1)
–> produced in many tissues, mainly liver
GH has both direct effects and IGF1 mediated effects
GH effects
Increase basal metabolism
Promotes growth of long bones
Stimulates muscle growth and protein synthesis
Both GH and IGD1 affect glucose homeostasis
GH on glucose homeostasis
Increases hepatic glycogenolysis
Increases lipolysis
Reduces peripheral glucose intake
IGF1 on glucose homeostasis
Similar to insulin
Stimulate peripheral glucose uptake
Stimulate glycogen synthesis
GH excess in childhood
Gigantism
GH excess in adulthood
Acromegaly
Acromegaly signs and symptoms
MSK Cardiovascular Metabolic Skin General Local tumour effects
Acromegaly symptoms- MSK
Protruding mandible (prognathia) Large tongue (macroglossia) Enlarged forehead (frontal bossing) Large hands and feet Carpal tunnel syndrome OA from abnormal joint loading
Acromegaly symptoms- CV
Dilated cardiomyopathy–> leading cause mortality in acromegaly patients
Cardiac failure
Hypertension
Acromegaly symptoms- metabolic
Impaired glucose tolerance
Potentially secondary diabetes
Acromegaly symptoms
Excessive sweating
Thickened, greasy skin
Acromegaly symptoms- General
Headaches
Tiredness (often v. debilitating)
Acromegaly symptoms- local tumour effects
Optic chiasm and visual field defects Cavernous sinus (CN III, IV and VI)
Acromegaly Investigations
Oral glucose tolerance test
MRI pituitary
Insulin tolerance test
Acromegaly- OGTT
Growth hormone fluctuates so much hard to test on its own
GH usually suppressed by eating
Unsuppressed GH levels after 75 glucose implies GH excess
Acromegaly- insulin tolerance test
GH released in response to hyoglycaemia
Acromegaly- management
Trans-sphenoidal surgery may be curative- 1st line if appropriate
Medical
External beam radiotherapy if medical management not effective
Acromegaly- medical managment
Somatostatin analogue- Octreotide
Dopamine antagonists (e.g. bromocriptine) may be of benefit, especially when tumour co-secreting prolactin
GH receptor blocker (Pegvisomant)
Dopamine antagonist
Bromocriptine
Somatostatin analogue
Octreotide
GH receptor blocker
Pegvisomant
Bromocriptine
Dopamine antagonist
Octreotide
Somatostatin analogue
Pegvisomant
GH receptor blocker
Acromegaly management
Link between acromegaly + development of colonic polyps –> increased risk bowel cancer
Patients should have colonoscopy at diagnosis
Surveillance colonoscopy for those with GH excess
