pituitary gland Flashcards
what is the anatomy and the surrounding structures of the pituitary gland ?
sits in the small cavity of the stella turcica
connected to the median eminence of the hypothalamus through the pituitary stalk
right above the pituitary is the optic chiasm
what does the posterior pituitary secrete ?
supra optic: vasopressin
paraventricular: oxytocin
what is the posterior pituitary derived from ?
neural ectoderm
what is the anterior pituitary gland deried from ?
rathkes pouch
what are the hormones secreted from the anterior pituitary ?
ACTH
TSH
LH and FSH
GH
prolactin
what is the main blood supply of the APG ?
hypothalamic portal system
what are the hormones responsible for the release and inhibitoon of prolactin and GH and TSH ?
dopamine : prolactin
somatostatin : GH , TSH
what is the function of prolactin ?
regulates milk production in mothers
associated with decreased GnRH , and works as a natrual contraception
what happens to prolactin levels upon destruction of the hypothalamus ?
prolactin levels increase
how does dopamine work in relation to prolactin ?
hypothalamus releases dopamine
dopamine inhibits lactotrophs via binding to D2 receptors
hw is hypothyroidism associated with hyperprolactinemia ?
TRH stimulates the anterior piruitary to release both prolactin and TSH
hence the hypothyroidism
what is the effect of pregnancy on prolactin ?
1- estrogen stimulates the release of prolactin release
2- prolactin inhibits GnRH - hence the cessation of ovulation and menustration
3- stimulates the growth of the mammary glands
why is there no milk production during pregnancy ?
due to high levels of estradiol and progesterone - block prolactin effect on milk
after childbirth the levels of estradiol and progesterone drop
what are the dopamine agonisits ?
bromocriptine and cabergoline
what are the clinical uses of dopamine agonists ?
used to treat parkinsons
prolactinomas ( viad D2 receptor binding )
what is the most common type of pituitary adenoma ?
prolactinoma
what are the symptoms of pituitary adenoma ?
these are general symptoms
headache
bitemporal hemianopia - due to compression on the optic chiasm
what are the symptoms of high prolactin levels in men vs women ?
women - amenorrhea , galactorrhea
men - hypogonadotrophic hypogonadism, so loss of libido and impotence
what are the side effects to using dopamine antagonists ?
parkinsonian symptoms
what are the different causes of hypopituitarism ?
either by a mass ; craniopharyngioma or a nonfunctional adenoma
or by ischemia
what are the levels of ACTH in association with hypopituitarism ?
low ACTH - and so low cortisol
there is no loss in aldosterone and so no salt wasting is seen
lack of hyper pigmentation
what is a craniopharyngioma and what is seen on imaging ?
a benign tumor that happens in children that is derived from rakthe’s pouch
on imaging a supra sellar mass with calcifications is seen
what are the symptoms associated with carniopharyngioma ?
hypopituitarism
headache visual field defects
behavioural changes
what is the empty sella syndrome ?
enlarged sella turcica filled with CSF
CSF causes compression on the pituitary gland
more common in obese women presenting with a headache
what is pituitary apoplexy ?
sudden hemorrhage into the pituitary gland
often occurs in a patient with pre existing adenoma
what is the presentation of pituitary apoplexy ?
sudden onset of severe headache
diplopia
hypopituitarism - which can appear in the form of shock
what is sheehan syndrome ?
enlargement of the pituitary gland due to increased hormone production
becomes more vunlerable to ischemia - after a traumatic labour
results in that all pituitary hormones are decreased in production
what is the presentation of Sheehan syndrome ?
can present as shock after delivery
can also present as failure to lactate
what is the only hormone increased in cases of sheehan syndrome ?
aldosterone
what is the treatment for hypopituitarism ?
hormone therapy
what is the other name for growth hormone ?
somatotropin
what are the stimulators of groeth hormone ?
exercise and sleep
GHRH
what are the inhibitors of growth hormone ?
glucose
somatostatin
IGF-1
what is the receptor for growth hormone ?
membrane bound receptor
once activated it activates JAK2
alteres gene expression
where are the growth hormone receptors found ?
the liver , which releases IGF-1
how can we measure the levels of growth hormone function ?
by measuring the levels of IGF-1
what are the direct effects of growth hormone ?
1- decreases glucose uptake by cells
also has an anti insulin effect
causes hyperinsulinemia
2- promotes lipolysis
what are the indirect effects of growth hormone ?
chondrocyte activation
increase muscle size
what are the causes of growth hormone deficiency ?
most commonly from a pituitary tumor
what is the treatment for growth hormone deficiency and how can it be monitored ?
treatment is synthetic growth hormone
monitored by the levels of IGF 1
what is the most common cause of growth hormone excess ?
somatotroph adenoma
what are the results of excess growth hormone in children vs in adults?
children : gigantism
adults : acromegaly
classic complaint of patients with acromegaly ?
gloves and shoes too small
rings dont fit
what other endocrine problem is associated with acromegaly ?
diabetes
due to insulin resistance
what is the cause of mortality in acromegaly ?
CV disease
how is a diagnosis of growth hormone excess measured ?
serum IGF-1 concentration
oral glucose tolerance test
what is the treatment for growth hormone excess ?
octeotride
which is a somatostatin analogue
what is MSH ?
stimulates melanocytes to produce melanin
shares the same precursor of ACTH (POMC)
what is the cause of hyper pigmentation in cushing disease ?
higher levels of MSH due to increased levels of ACTH
where is oxytocin produced ?
paraventricular nuclei of hypothalamus
what are the effects of oxytocin ?
causes milk release in response to suckling and induces uterine contraction
what is the ferguson reflex ?
an increase in cervical dilatation increases the uterine contractions this is associated with increased oxytocin release
where is somatostatin released from ?
D cells through out the GI tract
what is the function of somatostatin ?
inhibits the release of many hormones
inhibits growth hormone release
what is the association between dopamine and prolactin ?
dopamine inhibits prolacrtin
so with baby nipple stimulation - dopamine decreases , which in turn increases prolactin secretion
