anterior pituitary Flashcards by Alexi Cross

What hormones are produced by the anterior pituitary gland?

ACTH, TSH, FSH/LH, PRL

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What is the target organ for ACTH?

Adrenal Glands

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What is the secretory cell type for ACTH?

Corticotropic

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What is the function of ACTH?

increased cortisol, synthesis of adrenal proteins and maintenance of the adrenal gland.

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What is the secretary cell type for GH?

Somatotropic

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What are the two sections of target organs for GH?

1- Muscle, bone, and 2- liver

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What are the three parts of the adenohypophysis?

pars distils, pars tuberalis and pars intermedia

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How much of the adenohypophysis does the pars distalis make up?

90%

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Where is pars tuberalis?

wraps around the pituitary stalk

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what are the characteristics of pars intermedia?

regresses and is absent in adult human cells

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What are all endocrine functions in PG regulated by?

Hypothalamus and via negative and positive feedback

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What type of hormones are most APG hormones?

proteins and peptides

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What two hormones do NOT act through second messenger systems?

GH and PRL

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What are the functions of GH in muscle and bone?

regulates metabolic processes related to growth and adaption

muscle growth

increased protein synthesis

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What are the functions of GH in the liver?

increases liver glycigenolysis, induces foration of somatomedins and IGFS

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What is the secretory cell type for Prolactin?

lactrotropic

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What is the target tissue for Prolactin?

breasts

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What is the secretory cell type for TSH?

thyrotropic

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what is the target organ for TSH?

thyroid gland

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What are the functions of TSH?

increased secretion/production of TH

Increased iodide uptake

promotion of thyroid gland hypertrophy and hyperplasia

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What is the secretory cell type for LH and FSH?

Gonadotropic

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What are the target organs for LH and FSH?

LH and FSH in women: granulosa cells

LH in men: leydig cells

FSH in men: Sertoli cells

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What are the functions of LH?

ovulation, progesterone production, testicular growth and testosterone production.

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What are the functions of FSH?

Folicale maturation, estrogen production and spermatogenesis

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What does Corticotropes stimulate?

Adrenal Cortex

What are Corticotropes AKA?

POMC cell

What is the mechanism of action for ACTH?

ACTH binds to MC2R which is a GPCR. Activates Gs-cAMP-PKA pathway

What are the three main actions of ACTH?

1- increases cortisol and adrenal androgen production 2- increases steroidogenic enzyme production 3- promotes the growth of 2 zones in the adrenal cortex

What is ACTH regulated by?

Hypothalamic CRH

Describe the synthesis of ACTH.

synthesised in corticotropes by posttranslational cleavage of POMC

Describe the pattern of ACTH release.

Diurnal (every 24hrs) and peaks early in the morning

What are the stimulatory factors of ACTH?

Emotional, metabolic and physical stress as well as infection and inflammation

What class of hormone is TSH

Glycoprotein

What are the three glycoprotein hormones?

TSH, FSH and LH

Describe the heterodimer composition of TSH.

heterodimer= protein composed of two polypeptides a-subunit (common in FSH, and LH as well) b-subunit - specific and creates its difference

Describe the mechanism of action for TSH

binds to TSH receptor on thyroid epithelial cells --> linked to GPCR complex --> Gs-cAMP-PKA signal pathway

Describe the tropic (affect target cell by stimulating another target cell) effect of TSH.

Strong- stimulates hypertropy, hyperplasia and suvical of thyroid epithelial cells

When areTSH levels elevated?

low iodide availability = negative feedback

What is the thyrotrope stimulated by?

TRH

Describe the negative feedback of T3 on thyrotropes and TRH neurons.

T3 inhibits TRH and repesses b-TSH expression

What cell-secreting types is a dual hormone producer What two hormones doe they secrete?

Gonadotropes- FSH and LH

What do the gonadotropes regulate?

function of gonads in both sexes

Describe the mechanism of action for FSH and LH.

Bind ro respective receptors which are both part of GPCR --> cAMP-PKA pathway

What regulates FSH and LH?

GnRH

In what manner is FSH released?

In a pulsatile manner

What negatively feedback in men (Gn)

testosterone and estrogen

What negatively feedbacks in FSH secretion for men and women

Inhibin

At a low dose: estrogen

causes negative feedback on FSH and LH secretion

At a high dose: estrogen (what does it cause, when and what type of feedback)

causes surge of LH (ovulation = postive feedback)

What predominantly stimulates GH secretion and via what hormone

Hypothalamus via GHRH

What is an inhibitor of GH?

Somatostatin

What is a stimulator of GH?

GHRH

What does PRL act on (different from all other APG hormones)

non-endocrine cells to create a physiologcal change

What controls the production and secretion of PRL?

inhibitory conrtol via dopamine

What stimulates PRL and what Inhibits it?

S= TRH I=Dopamine

What does the disruption of the pituitary stalk and hypophyseal portal vessels result in? why?

INCREASE in PRL levels and DECREASE in ACTH, TSH, LH and GH? The sceretion of all others in prevented but as no dopamine, the PRL will secrete.

What is the mechanism of action for PRL?

JAK-STAT signalling pathway PRL binds to receptor in mammory glands --> Tyrosine Kinase Activation occurs --> transcriptioal regulation --> synthesis of milk

What is the main action of PRL

Breast development and milk production

What is the effect of PRL during puberty?

stimulates growth of alveolar component of breast tissue

What is the effect of PRL during pregnancy?

final alveolar and ductal development of breasts

What are high prolactin levels in prganancy promoted by?

estrogen

What is the effect of PRL after birth?

Suckling promotes its synthesis and release

What happnes to GnRH is PRL is increased

it decreases

What are the stimulatory factors of PRL?

Pregnancy, breast feeding, sleep, stress. TRH and dopamine antagonist

What are the inhibitory factors of PRL?

Dopamine, Bromocripine (dopamine agonist), somatotatsin and PRL (negative feedback loop)

What are the two main Anteriror piturtary disorders

Hyper and hypo secretion

What are the visual field defects for APG disorders, How are they invetsigated?

unexplained visual feild, consider due o pituitray or hypothalamic disorder until proven not and use opthalamolgical evaltions, neuro radiological studies and prolactin measurements.

What might hyperpituitarsm be due to?

over activity of gland or a adenoma

what is the most common cause of hypopituitarism?

compression of PG by non-secretory P macroadenoma

What is the neumonic for the sequnce pf hormone oss for hypopituritarsim?

Go Look For The Aderonoma

What are the two pituitary adenomas?

Macro and Micro

What is Panhyopopituitarsim

complete abesne of P hormones

What APG hormones do basophils secrete?

TSH, FSH, LH and ACTH