Growth hormone Flashcards
metabolic function of GH
promotes lipolysis and is counter-regulatory for hypoglycemia
mechanism of action
cytokine receptor activates JAK-STAT pathway
Laron’s dwarfism
inactivating mutation in GHR; treatment with IGF-1
direct actions of GH
opposes insulin, synergizes with cortisol
indirect actions of GH
dependent on IGF-1; IGF-1 has spillover with insulin and will activate insulin receptors (countering the effects of GH) at high enough levels
hypothal
positive: GHRH
negative: somatostatin
ant. pit.
40% of the cells here are somatotropes
release is pulsatile (more release during sleep)
feedback reg.
IGF-1 receptors at pituitary and hypothalamus
physiological stimulants of GH release
alpha-adrenergics; protein rich meal, hypoglycemia, stress, exercise, sleep
physiological inhibitors of GH
glucose, fatty acids and beta-adrenergics
acquired GH deficiency
traumatic brain injury, infection, iatrogenic (most common, esp. following resection)
genetic GH deficiency
defects in HESX1, PIT1, PROP1
clinical manifestations children (deficiency)
impaired growth; measured as >2 SD below normal, delayed bone age; hypoglycemia
clinical manifestations in adults (deficiency)
insidious, increased bone mass and adiposity
diagnosis of GH deficiency
based on provocative testing
arginine (protein load), clonidine (alpha agonist), insulin (induces hypoglycemia)
clinical manifestations children (excess)
gigantism, glucose intolerance
clinical manifestations adults (excess)
acromegally, arthralgias, glucose intolerance, hypertension
diagnosis of GH excess
elevated IGF-1, oral glucose tolerance test (failure to respond is indicative of GH adenoma), MRI for adenoma,
treatment for GH excess
transphenoidal surgery, or radiation + medical therapy if surgery is not successful
somatropin indications
GH deficiency
stature conditions: (Turner syndrome, chronic renal disease)
somatropin contraindication
any active malignancy
critically ill patients
somatropin dosage
SQ injection @ bedtime; considerably higher dose than normal
adverse effects somatropin children
headache, increased ICP, SCFE (all generally rare)
adverse effects somatropin adults
edema, arthralgias, carpal tunnel syndrome (adjust levels to keep them healthy)