the pitutary gland Flashcards
what is a hormone
Hormones
2 diff type of hormones
peptide and steriod
how are peptide hormone sythesised
Synthesised as prohormones requiring further processing (e.g. cleavage) to activate
storage
Stored in vesicles (regulatory secretion)
Receptors
Bind receptors on cell membrane and transduce signal using 2nd messenger systems
how are steriod hormones sythesised
Synthesised in a series of reactions from cholesterol
Storage
Released immediately (constitutive secretion)
Receptors
Bind to intracellular receptors to change gene expression directly
where does the pituitary gland sit
Sella turcica (of sphenoid bone)
what dictates the secreation of the anterior pituitary gland
hypothalmus
function of Hypothalamic parvocellular neurons
regulate anterior pituitary function
are they long or short
short
where di they terminate
median eminence
what do they relase
Release hypothalamic releasing/inhibitory factors
where do they release
capillary plexus in median eminence
where do they go
hypothalamic regulatory factors carried by portal circulation to anterior pituitary
what are endocrine cells
release hormones
what is Anterior pituitary also known as
adenohypophysis
made up of
Made up of endocrine cells:
how many
5 type
what are they
Somatotrophs Lactotrophs Corticotrophs Thyrotrophs Gonadotrophs
Regulated by
hypothalamic releasing/inhibiting factors via hypophyseal-pituitary portal system
what does the ant P rely on
hypothamus, hypothalmo-pitutary portal system
outline the steps in the Hypothalamo-pituitary portal system
Axon terminals of hypothalamic neurosecretory cells release hormones (RHs and IHs) into the
hypothalamo-pituitary portal system
The RHs and IHs travel in the portal system to the anterior pituitary
The RHs and IHs stimulate or inhibit the release of hormones (black dots) from anterior pituitary cells
Anterior pituitary hormones leave the gland via the blood
example using regulation of thyroid hormone
Axon terminals of hypothalamic neurosecretory cells release Thyrotrophin Releasing Hormone (TRH) into
hypothalamo-hypophysial portal system
TRH travels in the portal system to the anterior pituitary
TRH stimulates the release of Thyroid Stimulating Hormone (Thyrotrophin) from anterior pituitary thyrotrophs
TSH leaves the gland via the blood to travel to the thyroid gland to stimulate thyroid hormone release (thyroxine)
what do SOMATOTROPHS release
Growth hormone
Somatotrophin
LACTOTROPHS
Prolactin
THYROTROPHS
Thyroid stimulating hormone (TSH) (Thyrotrophin)
GONADOTROPHS
Luteinising hormone (LH) Follicle stimulating hormone (FSH)
CORTICOTROPHS
Adrenocorticotrophic hormone
ACTH, corticotrophin
what hormone released by the hypothalmus stimulates release of Growth hormone
GROWTH HORMONE RELEASING HORMONE
what inhibits GH
SOMATOSTATIN
how is Prolactin regulated
only inhibited by dopmaine
Thyroid stimulating hormone (TSH) (Thyrotrophin)
THYROTROPHIN RELEASING HORMONE
Luteinising hormone (LH) Follicle stimulating hormone (FSH
GONADOTROPHIN RELEASING HORMONE
Adrenocorticotrophic hormone
ACTH, corticotrophin
CORTICOTROPHIN-RELEASING HORMONE
where is/are the receptor/s for growth hormone
liver, muscles, bone
mainly liver
Prolactin
Breasts
lactating women
Thyrotrophin
Thyroid
Gonadotrophins
Testes (males)
Ovaries (females)
Adrenocorticotrophic
hormone
Adrenal cortex
what is bitemporal hemianopia
Loss of outer part of visual field
caused by
Compression of the optic chiasm by a pituitary tumour
what occurs at optic chiasm
Fibres from the nasal (medial) retinae cross at the optic chiasm
so why
tumour prevents transmission of sensory information from lateral visual fields to the occipital lobe
What is the name of the bony dish that the pituitary gland sits in?
Sella turcica
does m production involves the posterior thalmus
yes involves both anterior and posterior
Neuroendocrine reflex arc: milk production
Mechanical stimulation of nipple & surrounding area activates afferent pathways
Afferent signals integrated in the hypothalamus and inhibit dopamine release from dopaminergic neurons
Less dopamine in the hypothalamic-pituitary portal system causes less inhibition of anterior pituitary lactotrophs
Increased plasma prolactin increases milk secretion in mammary glands
relationship between prolactin and dopamine
dopamine inhibts prolactin
more dopamine less prolactin
mechanism of action of growth hormone
direct
GH released from Anterior pituitary
can bind directly GH receptors on body tissue
indirect
bind to GH recepto on liver
stimulate release of IGF 1
binds to IGF 1 recptors
IGF 2
more important in developing featus
a tumour of PG can also cause
to much growth factor or other type of hormone
before p
if you have that (too much GH from tumour) before puberty- you have gigantism (the thing hasn’t fused at the end of bones) epiphyseal growth plate
after
you wont grow
what happens
Acromegaly (excess growth hormone)
Symptoms
Coarsening of facial features Macroglossia (larger tongue) Prominent nose Large jaw - prognathism Increased hand and feet size Sweatiness Headache Acromegaly does NOT result in increased height
The posterior pituitary gland is called
neurohypophysis
made up of
neuronal tissues
what is a nuclues in the hypothalmus
collection of neuronal cell bodies
what is the blood supply like in the posterior pituitary gland
No blood supply
releases
Arginine vasopressin (AVP) (also known as Anti-diuretic hormone) Oxytocin
how is it connected to hypothalmus
Posterior pituitary is anatomically continuous with hypothalamus
Hypothalamic magnocellular neurons:
Long, originate in supraoptic (AVP) and paraventricular (oxytocin) hypothalamic nuclei
Nuclei → stalk →posterior pituitary
Regulation of the posterior pituitary gland
pathway
Two sets of hypothalamic neurosecretory cells produce AVP and oxytocin and transport them to the posterior pituitary
(Posterior pituitary hormones:
Arginine vasopressin (AVP) (also known as Anti-diuretic hormone)
Oxytocin)
Excitation of these hypothalamic magnocellular neurons stimulates release of AVP or oxytocin into the posterior pituitary where they diffuse into blood capillaries…
…then leave the posterior pituitary via the blood
what does vasopressin cause
stimulation of water reabsorption in the renal collecting duct
This concentrates urine
what other functions
Also a vasoconstrictor (via V1 receptor)
Stimulates ACTH release from anterior pituitary
how does it work
AVP binds to v2 recptor
Stimulates intracellular signilling cascade
Causes aqua porin 2 to fuse to apical membrane
Water is then reabsorbed to the systemic circulation
Exits through aqyaporin 3 receptors to the blood
function of oxytocin
Delivery of baby
Milk ejection
how does it cause DOB
CONTRACTION
of Myometrial cells
and ME
CONTRACTION
Myoepithelial cells
Neuroendocrine reflex arc – milk ejection
Mechanical stimulation of nipple & surrounding area activates afferent pathways
Afferent signals integrated in the hypothalamus and stimulate oxytocin-releasing neuron activity
Action potentials travel down oxytocin neurons and oxytocin is secreted into the bloodstream
Increased plasma oxytocin increases milk ejection in mammary glands
which 2 hormones stimulate ACTH
CRH AVP
both anterior and posterior
What questions would you ask a patient in whom you suspect a diagnosis of acromegaly?
Have they grown in shoe size
does their wedding ring still fit
do they feel their tongue has got bigger
can they bring and show old photos of them(photo album or phone)
do they have diffculty chewing or swallowing
signs vs symptoms
sympotms subjective- like fatigue
signns- obvious like rash
what causes sweatiness in acromegaly
growth factors
how to test bitemporal hemianopia without special eqiupment
ask patient to close one eye.
ask them to look at your nose
starting from the side of youre head, bring you hand to wards the nose and see when they can see your hand
what is a Portal system
portal at both ends
how to detect if levels are too high
suppress the hormone in question
for acromegaly
Need to give a growth suppressor- glucose
A large dose-
Stop making growth hormone
Oral glucose tolerance test
