ENDO Week 4 Flashcards
What kind of hormones do the anterior pituitary (AP) release?
Proteins (or peptides)
They act through second-messenger systems (except GH and prolactin).
What 3 parts is the anterior pituitary (AP) formed from?
The pars distalis, the pars tuberalis, and the pars intermedia.
What is the pars distalis?
It makes up about 90% of the adenohypophysis.
What is the pars tuberalis?
It wraps around the stalk.
What is the pars intermedia?
It regresses and is absent in adult humans.
which cell types are acidophils
somatotrophs
lactotrophs
which cell types are basophils
Thyrotropes
Gonadotropes
Corticotropes
how do acidophils stain
Stain well with acidic dyes such as eosin
how do basophils stain
Stain well with basic dyes (e.g., hematoxylin)
what do corticotropes release? stimulate? what are they cleaved from?
releases ACTH (peptide) from CRH
stimulate the adrenal cortex
cleaved from POMC
what pathway does acth use on adrenal cortex cells
cAMP
what is acth’s effect
Increases cortisol from adrenal cortex and androgen production from adrenal medulla
Promotes growth and survival of the adrenal cortex
what causes hyperpigmentation
too much acth
binding MC1R
what is ACTH diurnal rhythm
Peaks in the morning 3-4am
Increasing in cortisol after that in the early morning 6-8am
is ACTH tropic or trophic
both
what neurone are stimulated to release acth in high stress
parvicellular
is ACTH bound or unbound in blood
circulated unbound
what do thyrotropes release? stimulate?
releases TSH from TRH (glycoprotein)
stimulates thyroid gland
does TSH travel bound or unbound
unbound
what is TSH mechanism of action
cAMP pathway on thyroid epithelial cells
is TSH tropic or trophic
both
Stimulates thyroid to release hormone (t3 and t4)
stimulates thyroid for glandular growth
describe the negative feedback system for TSH
T3 (the active form of TH) can negatively feedback on AP (pituitary thyrotropes) and hypothalamus (TRH producing neurons), inhibits TRH production and secretion
what are the three glycoprotein hormones
TSH, FSH and LH
describe the subunits of the glycoprotein hormones
composed of an an alpha subunit: α - GSU
and a β-subunit (β - ?)
β- subunit is specific to the hormone (β - TSH, β - FSH, and β - LH)
what do gonadotropes release? stimulate?
releases FSH and LH from GnRH
stimulates ovaries and testes
how do FSH and LH travel
unbound
in which manner are FSH and LH secreted
pulsatile
what are FSH and LH effects?
secretion of testosterone in men
estrogen and progesterone in women
what are the different effects of estrogen in a low and high concentration?
low concentration = negative feedback on FSH and LH
high concentration = increase LH causing ovulation (pos feedback)
what do somatotrophs release? stimulate?
secretes GH from GHRH, stimulates all areas of the body
major target is liver for IGF-1 (part of the hypothalamus-pituitary-liver axis)
what is GH pathway?
JAK STAT
no second messenger
what do lactotrophs secrete? stimulate?
secrete prolactin (protein)
stimulate breast milk production in mammary glands
how is PRL different from other hormones
no axis
(hypothalamus-pituitary-…)
Acts directly on non-endocrine cells to induce physiologic changes
how is PRL inhibited
GHIH and dopamine
how is PRL stimulated
TRH and estrogen
what effect would damage on hypothalamus have on PRL secretion
results in an increase in PRL levels, but a decrease in ACTH, TSH, FSH, LH, and GH
how does PRL travel
unbound
what pathway does PRL use
JAK STAT no second messenger
describe how prolactin inhibits ovulation
Prolactin can inhibit GnRH secretion, decreasing LH and FSH ,decreasing estrogen and progesterone
No LH peak = no ovulation
ex: during breastfeeding
what is an adenoma
glandular tumor
what is a micro and macro adenoma
micro= less than 10mm
macro= more than 10mm
what is a pituitary adenoma
benign tumour of the anterior pituitary
what can a pituitary micro adenoma cause
hormone hyper secretion
what can pituitary macro adenoma cause
hormone hypo or hyper secretion
can cause hypopituitarism due to compression of normal pituitary tissue
what is hyperpituitarism caused by
Caused by secretory adenoma or overactivity of gland
what are some effects of hyperpituitarism
- Excessive serum concentration of pituitary hormone (GH, PRL)
- Morphologic and functional changes in the anterior pituitary
what is hypopituitarism cause by
Caused by non-secretory adenoma (causes pressure) or damage to hypo or ap
what can hypothalami-pituitary lesions cause
-Pituitary hormone hypersecretion and hyposecretion
-Sellar enlargement
-Visual loss and headache = prolactin levels to be checked because prolactin is the most present in ap
what is a prolactinoma
Specific type of pituitary adenoma that overproduces the hormone prolactin
what is hyperprolactinemia caused by and what are its effects
Caused by pregnancy/breastfeeding or prolactinoma & damage to hypothalamus/ap
Decreases FSH and LH, could cause amenorrhea
what is micro and macro prolactinoma
micro = tumor less than 10mm
micro = tumor more than 10mm
what is panhypopituitarism and what is caused by
- Inadequate production of all ap hormones
-Can result from damage hypothalamus and ap or pituitary hormones
what is the effect of prolactin on a man
Increased prolactin
–> decreased GnRH
–>Decreased LH and FSH –> decreased testosterone
resulting in decreased spermatogenesis and decreased libido
what are the consequences of hypothalamic, pituitary and glandular failure
Hypothalamus failure –> low pituitary hormone and low target hormone
Pituitray failure –> low pituitary hormone and low target hormone
Target gland failure –> low target hormone, high pituitary hormone and high hypothalamic hormone
provide an example of negative feedback
- Hypothalamus
Releases CRH and acts on hypothalamus (ultra short loop) - Anterior pituitary
Releases ACTH and acts back to hypothalamus (short loop) - Adrenal cortex
Releases cortisol and acts back to ap or hypothalamus (long loop)
what is the flow for hypercortisolism
decrease cortisol
increased ACTH
triggers MC1R
causes melanocyte stimulation
increase melanin production
results in hyperpigmentation
