Hypothalamus and Pituitary Tutorial Flashcards
what is a ENdocrine gland
secretes its hormones directly into the bloostream
what is an EXocrine gland
secrete their hormones into a collection of ducts which are carried around the body
what is the difference in onset and duration of action of endo vs exocrine glands
exocrine quicker response
endocrine longer duration as taken to kidney to made available for absorption
match each hormone to its class:
steroid
protein and peptide
amine
insulin
adrenaline
testosterone
steroid- testosterone
protein and peptide- insulin
amine- adrenaline
true or false- amine peptides and proteins are only synthesised on demand
false
true or false- steroid hormones are mainly bound to proteins in the plasma
true
true or false- amines, peptides and proteins stimulate and act on intracellular receptors
false - have cell surface receptors
list these from shortest to longest half lives:
steroid
amine
peptide
amine- seconds
peptide- minutes
steroid- hours
what connects the hypothalamus to the pituitary
the pituitary stalk
what is the adenohypophysis
anterior pituitary
what in the neurohypophysis
posterior pituitary
what synthesises posterior hormones in the hypothalamus
supraoptic and paraventricular nuclei (neuroendocrine)
how do hormones from the hypothalamus get to the anterior pituitary
cell bodies secrete into via portal veins
what are the ‘releasing’ stimulatory hypothalamic hormones
growth hormone releasing hormone (GHRH) prolactin releasing hormone (PRH) thyrotrophin releasing hormone (TRH) corticotrophin releasing hormone (CRH) gonadotrophin releasing hormone (GnRH)
what are the inhibitory hypothamalic hormones
somatostatin and dopamine
what class are the hypothamalic hormones
all peptides except dopamine which is an amine
what does dopamine inhibit
the release of prolactin (ant pit)
what does somatostatin inhibit
growth hormone (ant pit)
what is released from the anterior pituitary
GH ACTH (andenocorticotrophic hormone) TSH PRL FSH (follicle) LH (lutenising)
what is released from the posterior pituitary
oxytocin
anti-diuretic hormone (ADH)
what is the function of oxytocin
milk secretion and uterine contractions
what is the function of ADH
increases water reabsorption at kidneys
vasoconstriction at vascular smooth muscle
what are the actions of growth hormone
increases blood glucose by increasing gluoneogenesis in the liver
releases insulin GF (IGF-1) from the liver
decreases glucose uptake in muscles cells- increases it in brain cells
increases the rate of lipolysis in fat cells
has anabolic effect on the body
increase glucose and fatty acids
increased protein synthesis
decreased fat storage
increased soft tissue growth
increased bone growth
what are common conditions in growth hormone excess
diabetes (T2), carpal tunnel syndrome, hypertension
what does IGF-1 cause
increased bone growth
increased soft tissue growth
increased protein synthesis
what changes can be seen in acrogmegaly
increase in hand and foot size prominent brow large nose and jaw pronounced cheekbones skin changes (thickens, sweating, acne) oral manifestations (enlargement of tongue and swelling of larynx, interdental separation)
how can acromegaly’s oral manifestations cause presentations
deep or coarser voice
obstructive sleep apnoea
how is movement affected in acromegaly
joint pain, proximal muscle weakness, lethargy decreases movement
decreased movement in hands and pain/ tingling sensations
what behavioural problems arise in acromegaly
lethargy
polydispsia and uria
why do you get hypertension in acromegaly
increased plasma fatty acids causes patty plaques
what nerve is affected in carpal tunnel
median nerve
what provides negative feedback for GH
IGF-1 negative on ant pit
GH negative on Hypothalamus
what causes acromegaly
pituitary tumour (micro <1cm or macroadenoma >1cm) ectopic tumour
what is gigantism
when children have a growth hormone secreting tumour of the pituitary gland- epiphyseal plates not closed so large bone growth
in acrogmegaly what hormone can also be secreted in excess
prolactin (in one 1/3rd of patients)
why can GH nnot diagnose acromegaly
as released in pulsatile manner - highest when asleep and in times of stress
when is growth hormone low normally
in pregnancy
what is the definitive test for acromegaly
oral glucose tolerance test
how does oral glucose tolerance test diagnose acromegaly
oral glucose should suppress GH to <1 microgram/litre
if no suppression then acromegaly
what can IGF-1 test show
mean 24 hour secretion of growth hormone
what scan is done to see if there is a tumour in acromegaly
MRI of the pituitary fossa
what is the treatment for acrogmegaly
surgery- trans-sphenoidal
radiotherapy- (with/without surgery)
dopamine agonists (bromocriptine and cabergoline)
somatostatin receptor agonists (octreotide and lanreotide)
growth hormone antagonists (pegvisomant)- works on GH receptors not on tumour
what can cause hypopituitarism
pituitary tumour
radiation damage
trauma
infective (meningitis, syphilis, encephalitis)
immunological (autoimmune)
infiltrative (haemachromoatosis, sarcoidosis, secondary mets lesions)
