Physiology: Endorcine #7 - Hormones Of The Pituitary

Front 1

what neurohormones are made by the hypothalmus and transmitted to the pituitary?

Back 1

ADH and oxytocin are neurohormones made in the hypothalmus (in the hypothalamic neurocrine cells) and sent, via nerves, into the posterior pituitary (neurohypophesis)

also, there are neurohormones made in the hypothalmus that are targeted to the median emminence, which are eventually destined for the anterior pituitary. these are the "RH" releasing hormones.

Front 2

how similar are oxytocin and ADH?

Back 2

very close.

they differ at 2 of their 9 amino acids. this means they have similar effects

Front 3

what else is packaged with ADH and oxytocin?

Back 3

the pre/pro clipped off parts are called NEUROPHYSIANS - they aren't biologically active but seem to have an important role targeting the hormones from the neuroendocrine cells to the posterir pituitary.

Front 4

what else is ADH known as? what receptors does it work on? what factors regulate it?

Back 4

AVP (argenine vasopressin)

works on V1 and V2 receptors.

It's primarily activated by osmolarity (increased = increased secretion). also by volume (hypOvolemia = more secretion).

also by the osmolarity of CSF (increased secretion).

also by temperature (high temperature = more secretion)

Front 5

ADH - what receptors does it work on and what second messengers does it work through?

Back 5

V1 and V2 receptors.

V1 are on blood vessels and cause VASOCONSTRICTION (makes sense if you're trying to retain water). This works through Ca++/IP3.

V2 receptors are on the collecting duct and increase H20 resorption, these work through cAMP.

just in case someone asks, V2 is also vasodilatory according to pandey, which seems weird.

Front 6

what's the main effect of oxytocin? when do you give oxytocin?

what secondary messanger does it work through

Back 6

let down in breast feeding. this happens through myoepithelial constriction to make milk go from the alveoli into the ducts.


ALSO - causes SM contraction in the uterus

so, it's used as a drug to induce labor and to stop bleeding after labor.

works through Ca++/IP3

Front 7

what releases oxytocin? inhibits?

Back 7

uterine/genital stimulation. also, suckling.



opoids inhibit release.

also, catecholamines can counteract effects.

Front 8

anterior pituitary - what factor causes differentiation of a lot of these cells?

what anterior pituitary hormones are secreted in a pulsatile fashion?

Back 8

Pit-1

all are secreted pulsatorily.

Front 9

if you mess with pulsatility, what diseases should we think of?

Back 9

Cushing's syndrome comes from non-pulsatile release of corticotropin (the circadian rhythm of it is messed up). Corticotropin = ACTH

ACROMEGALY - when the circadian pulsatile release of GH (aka somatotropin)

Front 10

Corticotropin - what is its precursor?

Back 10

ACTH (cortiocotropin) is a 39 amino acid molecule that's originally part of a 241 AA big protein called POMC (pro-opiomelanocortin) and gets cleaved ito ACTH.

Front 11

what turns on ACTH release? what turns it off?

Back 11

up regulated by CRH (corticotropin releasing hormone) and by ADH.

Turned off by BNP (brain-natureptic peptide).


cortisol (later released from the adrenal glands by ACTH stimulation) feeds back on both CRH release from the hypothalmus and on CRH receptors on the anterior pituitary.

Front 12

what is growth hormone similar to?

Back 12

looks a lot like prolactin, also like human placental lactogen (hPL, aka hCS = chorionic somatomammotropin).

Front 13

what are our glycoproteins released from the anterior pituitary?

what are some other names for these hormones?

Back 13

glycoproteins include the genital guys (FSH, LH) and thyrotropin (TSH).

other names:
FSH = follitropin
LH = lutropin
TSH = thyrotropin

Front 14

glycoprotein hormones - how are they structurally similar?

Back 14

they all have alpha and beta subunits.

their alphas are identical, their betas are different and confer their specific function.

Front 15

talk about LH and FSH in post-menopausal women

Back 15

FSH goes up, LH stays the same (note that for histo class, this isn't true - both go up, but FSH goes up more)

note that women tend to have larger gonadotrophs with more granules than men, and their shape changes throughout the cycle.

Front 16

GnRH, FSH, and LH : how is FSH or LH preferentially secreted when GnRH works on both?

Back 16

this is where the pulsatile action of GnRH comes into play.

GnRH pulses once an hour, maintaining LH and FSH release.

If you increase the GnRH pulse frequency, you preferntially increase LH secretion.

If you decrease GnRH pulse frequency, preferentially increase the release of FSH.

Think that girls prefer things slower.

Front 17

what feeds back on GnRH?

Back 17

estradiol and dihydrotestosterone decrease frequency of GnRH secretion, which tends to inhibit LH secretion (favors FSH)

Front 18

if you infuse lots of extra GnRH, what happens to LH and FSH?

Back 18

LH has the biggest change - it's got a biphasic change. First get a big increase in LH (remember, increasing GnRH frequency ups LH first). It then drops off for a bit, then spikes back up again later on (due to new synthesis).

FSH has a kind of steady, low level increase in response to GnRH introduction.

so, generally, when thinking about GnRH and LH/FSH secretion, think that LH is what responds to GnRH directly and rapidly - FSH kinda does mostly its own thing.

Front 19

pulsatility - LH, FSH, and testosterone - how does it look over time?

Back 19

LH varies dramatically with time, even over the course of a day. Because LH works to release testosterone, it peaks up and down constantly as well. the testosterone feeds back seriously on LH, contributing to the down peaks of LH.

FSH is kinda off in its own world, peaking up and down but at a much lower level.

Front 20

review:

Back 20

Testosterone and estradiol both feedback on LH in two ways: decreases pulses of GnRH (favoirng FSH) and on LH release from the anterior pituitary.