Pituitary physiology Flashcards
what is on the sides o pituitary
internal carptid arteries
what is above the pituitary
optic chiasm
below pituitary
sphenoid sinus
where is adh secreted from
posterior pituitary
where are most hormones secretd from
anterior pituitary
how are most hormones released
by an activating pathway
except for prolactin
how is prolactin inhibited
under tonic inhibition by hypothalamic dopamine
when do prolcatin levels rise
in pregnancy response to prolactin releasing hormone from hypothalamus
dynamic endocrine testing
○ Hormone excess - suppression test
Hormone deficiency - stimulation test
stimulatory tests
synacthen test
diagnostic procedure used to assess the function of adrenal glands and their response to ACTH
key components of synacthen test
synthetic form of ACTH
stimulates adrenal glands to produce cortisol
cortisol management: blood samples are taken to measure cortisol levels before and after synacthem administration
what is the posterior pituitary regulated by
alternative signals such as vasopressin, barcoreceptors
pituitary disease
too much hormone or too little if function is compromised
or glsnd too big
some tumours may be doing all three
optic chiasm
x shaped structure formed by the crossing of optic nervesw
when might the optic chiasm be compressed
due to pituitary tumours-loss of peripheral vision
why is acth a difficult hormone to measure
its unstable and easily degraded by enzymes
short half life of 10 min roughly
peak levels occur early in morning and lowest at night - requiring precise timing
indications for synacthen test
primary adrenal insufficiency- addisons - failure of adrenals themselves
secondary adrenal insufficiency- due to insufficient ACTH production by the pituitary gland
HPA Axis Assessment
to assess adrenal glands in response to stress
gold standard test for HPA axis assessment
insulin tolerance test
clinical features assoc with anterior pituitary deficiency
GrowthHormone;Growthhormonedeficiency(GHD)-growthfailure
- → TSH; hypothyroidism (secondary)
- → LH/FSH; Hypogonadism (hypogonadropic hypogonadism)
- → ACTH;hypoadrenal(secondary)
→ Prolactin;noneknown
clinical features assoc with posterior pituitary def
ADHdeficiency: Arginine vasopressin deficiency (diabetesinsipidus)
causes of hypopituitaryism
- Tumours - non pituitary and pituitary
- Brain damage
- Iatrogenic
- Infection
- Genetic
- Idiopathic
Granulomatous disease
replacement therapy for hypopituitarism
hydrocortisone
thyroxine
sex steroids
GH
ADH
testosterone replacement
skin gels
IM injection
prolonged IM injcetion
which hormone regulates ACTH production
corticotropin releasing hormone - CRH
which cranial nerve is most commonly affected by an enlarging pituitary gland
optic nerve - cranial nerve II
prolactin functions
lactation and reproduction functions
stimulates milk production in mammary glands after childbirth - increases in pregnancy to prepare breasts
regulates menstrual cycle
in men it influences sperm production and maintains overall reproductive health
