15-20% of anterior pit products: 1. ACTH --> adrenal gland 2. beta-lipotropin --> adipose and melanocytes

Pituitary Hormones Flashcards by Nick Mankowski

body functions dictated by the posterior pituitary gland

water balance

blood volume

intake - thirst

output - urine volume

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body functions dictated by the anterior pituitary gland

metabolic rate

stress response

growth

reproduction

lactation

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2 types of neurosecretory cells in hypothalamus

magnocellular

parvocellular

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median eminence

neurovascular region of hypothalamus

where neurohormones are transported to once made in the neuronal bodies

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corticotroph

15-20% of anterior pit

products:

ACTH –> adrenal gland
beta-lipotropin –> adipose and melanocytes

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thyrotroph

3-5% of anterior

TSH –> thyroid gland

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gonadotroph

10-15% of anterior

LH –> gonads

FSH –> gonads

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somatotroph

40-50% of anterior

GH –> all tissues

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mammotroph

10-25% of anterior

prolactin –> breasts, gonads

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how are anterior pituitary hormones secreted

pulsatile fashion

for efficient and effective signaling of target tissues for the ability to change the signal strength and regulating ongoing metabolic clearance of the hormone

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regulation mechanisms of anterior pituitary hormones

releasing and inhibiting hormones from hypothalamus

2. negative feedback mechanism

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corticotropin

39 amino acids

precursor molecule = POMC

first 18 amino acids have full biological activity…first 24 are identical across species

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modification of POMC

cleaved into beta-lipotropin, ACTH, and NH2-terminal peptide

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modification of corticotropin during fetal life and at end of pregnancy

cleaved into melanocyte stimulating hormone and cotricotropin like peptide (cotricotropin)

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modification of beta-lipotropin during fetal life and at end of pregnancy

split into lipotropin and beta-endorphin

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effect of stress and sleep-wake on ACTH secretion

- hypothalamus to secrete corticotropin releasing hormone (CRH)
- anterior pit to release ACTH
  - which negatively regulates CRH secretion from hypothalamus

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ACTH effect on adrenal gland

(+) cortisol release from adrenal gland

cortisol negatively regulates

CRH release from hypothalamus
ACTH release from anterior pituitary

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2 molecules released from hypothalamus that (+) ACTH release from anterior pituitary

CRH and ADH

molecule released from hypothalamus that (-) ACTH release from anterior pituitary

BNP

NE, ACh, and serotonin on hypothalamus

(+) release of ANP and CRH –> (+) ACTH

gamma-aminobutyric acid

endorphins

ACTH itself

cortisol

EFFECTS on hypothalamus

(-) release of ANP and CRH –> (-) ACTH

prolactin-GH hormone family

GH, hPL, hCS

share amino acid sequence homologies

can be divided into GH and prolactin sub-families

glycoprotein hormone family

FSH, LH, and Thyrotropin

each consists of 2 noncovalently linked subunits alpha and beta

alpha is common to all 3
beta is unique to each and confers specificity

alpha subunit is considered to be more abundant than the unique beta

FSH and LH levels after menopause

increase

general regulation of FSH and LH

integration of LHRH (GnRH) signal feedback effects of gonadal steroids peptide hormones (inhibin)

effects on gonadal steroids and peptide hormones on FSH and LH release without LHRH

ineffective...need LHRH to for those to have any effect at all

rate of LHRH pulse per hour for maintaining LH and FSH secretion

1 pulse per hour

when LHRH pulse frequency is decrease to 1 every 3 hours...

FSH secretion is preferentially stimulated

more frequent LHRH pulses...

initially increase frequency of LH pulse and mean LH concentrations

estradiol (ovaries) and dihydrotestosterone (testes)

negative feedback on LHRH (GnRH) release and thus reduce release of LH also inhibits FSH and LH release directly by (-) pituitary release

endorphin and Dopamine effect on hypothalamus in gonadotropin regulation

inhibits hypothalamic release of GnRH

NE effect on hypothalamus in gonadotropin regulation

stimualtes hypothalamic release of GnRH

Follistatin, Inhibin, and Activin

released from gonads (peptide hormones) upon FSH and LH stimulation follistatin --> (-) pituitary FSH inhibin --> (-) pituitary FSH and hypothalamus GnRH activin --> (+) pituitary for FSH

neurohormones secreted by posterior pituitary

ADH (AVP) oxytocin very close in structure (only 2 of the 9 amino acids are different..and same disulfide bond is present)

amino acid difference between ADH and oxytocin

ADH: X-X-Phe-X-X-X-X-Arg-X Oxytocin: X-X-lle-X-X-X-X-Leu-X closeness causes overlap in hormone effects

neurophysins

I = for OTC II = for ADH packaged and secreted with these...without them, the hormones remain in the secretary vesicles

four factors that regulate ADH secretion

osmolarity body fluid volume CSF concentration of Na+ changes in body temperature

osmoreceptors for ADH secretion

located in anterior hypothalamus...mainly on neurons of the OVLT as little as 1% rise in osmolarity will increase their firing and stimulate ADH producing neurons in the supraoptic nucleus and the paraventricular nucleus of the hypothalamus thereby increase plasma ADH

hypovolemia and ADH

increase ADH release with blood volume decreases by ~10% located in the right atrium

increase of Na+ in CSF

increases ADH via Na-sensors

ADH through V1 and V2 receptors

ADH acts on V1a receptors --> causes vasoconstriction V2 receptors (kidney) tend to counterbalance this effect do this to conserve water and regulate plasma tonicity

ADH effect on ACTH secretion

increases ACTH secretion --> (+) cortisol levels

ADH activation of V2 receptors in kidney tubule and cortical collecting duct cells causes antidiuresis in 3 ways

1. stimulate Na/K-2Cl co transport in the thick ascending limb 2. increase the permeability of the collecting duct to urea 3. increase permeability of the collecting ducts to water

body temperature on ADH secretion

increase = (+) ADH