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ER Week 1 > Intro to Endocrinology > Flashcards

Intro to Endocrinology Flashcards

1
Q

What are the three types of hormones?

A

peptide-protein
lipid
nonpeptide amino acid-based

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2
Q

True or false: hormones exert their effect only when they reach a high concentration.

A

false - work at very low concentrations

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3
Q

What are the three general types of effects hromones can have?

A

endocrine
paracrine
autocrine

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4
Q

What do free hormone need to bind to?

A

carrier proteins in the serum and free receptor to make a hormone-receptor complex (which does the actual signalling)

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5
Q

True or false: hormone-receptor binding is irreversible.

A

false - it’s reversible

but note that some of the drugs we use to counter this system are irreversible

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6
Q

Since there are only a limited number of receptors on a cell, the receptors are _____

A

saturable

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7
Q

Why can se way that hormones and receptors have varying levels of specificity?

A

because they may bind to multiple receptors with varying specificity and a given receptor may bind multiple hormones

the key is the varying specificity - the one with the highest specificity will get the strongest signal

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8
Q

What is the integrating controller of the endocrine system?

A

hypothalamus

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9
Q

What does the hypothalamus control?

A

pituitary gland, which then controls all the rest

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10
Q

What are the other endocrine glands?

A

pancreas, thyroid, parathyroid, adrenals, ovaries and testes

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11
Q

What part of the pituitary is a true endocrine gland and what is an extension of neural tissue?

A

anterior is the true endocirne gland of epithelial origin

the posterior is an extension of the neural tissue

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12
Q

What project into the posterior pituitary to trigger release of hormone?

A

hypothalamic neurons

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13
Q

What hormones are produced by those hypothalamic neurons in the posterior pituitary?

A

oxytocin and vasopressin

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14
Q

What is the advantage for this arrangement between the hypothalamus and posterior pituitary?

A

target cells see the stimulatory hormone very quickly - hugely important for both vasopressin and oxytocin

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15
Q

How is the axis arranged for the anteiror pituitary?

A
  1. hypothalamic nueonrs deposit hormones into the hypothalamo-hypophyseal portal system
  2. this system will bathe the pituitary cells in those hormones and hormones will bind appropriate receptors
  3. Ant pit cells will produce and release their hormone into general circulation
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16
Q

So is this slower or faster than with ht eposterior pit?

A

slower

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17
Q

Is most of the regulation of the hormone secretion negative or positive?

A

negative feedback

e.g., thyroid hormone curtails release of thyroid releasing hormone and thyroid stimulating hormone

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18
Q

Positive feedback is rare in this system, but what is an example?

A

snow ball effect from very high ovarian estrogen stimulating ovulation

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19
Q

What are the three groups of non-peptide amino acid derivatives?

A

thyroid hormones

catecholamines

tryptophan derivatives like melatonin

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20
Q

What are the two general lipid hormones

A

steroids and eicosanoids

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21
Q

In general how are protein/peptide hormones synthesized?

A

a preprohormone is synthesized and cleaved into prohormone in the RER

the prohormone goes to the golgi where further enzymatic cleavage occurs to produce th e mature hormone

it’s then packaged into secretory granules

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22
Q

In general, how are peptide hormones secreted?

A

upon apropriate signals, the secretory granules fuse with plasma membrane, releasing the hormone into the circulation

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23
Q

are protein hormones soluble in water?

A

yes

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24
Q

What’s the usual carrier protein that will carry and increase the total amount of hormone in the circulation

A

albumin

25
Q

Preprohormone for TRH is efficient because….

A

it’s cleaved down to 5-6 copies of TRH

26
Q

In genera, how are steroid hormones synthesized?

A

derived from cholesterol

converted to findal product by enzymatic action

enzymes are located in the mitochondria and smooth ER

27
Q

Is the steroid packaged and stored before it’s secreted?

A

nope - it’s produced and secreted right away

28
Q

Are steroid hormones soluble in water?

A

nope, so 99.9% will be bound to a transport protein

29
Q

What are most of the eicosanoids derived from?

A

arachidonic acid

30
Q

What enzyme will form the prostaglandins and thromboxanes?

A

cyclooxygenase

31
Q

What enzyme makes leukotrienes?

A

lipoxygenase

32
Q

What enzyme will make the epoxides?

A

cytochrome p450 mono-oxygenase

33
Q

Do eicosanoids work locally or at a distance?

A

only locally (and at low levels)

34
Q

What are three examples of catecholamines?

A

dopamine
norepinephrine
epinephrine

35
Q

What kind of receptor do the catecholamines bind to?

A

G-protein couple transmembrane receptors

36
Q

What are the two thyroid hormones?

A

T4 (thyroxine0

T3 (Triiodothyronine)

37
Q

In general, how is thyroid hormone synthesized?

A

syntesized on a protein backbone which is processed in lysosomes

38
Q

Control of production for thyroid hormone is based on what?

A

whehter the enzymes are available and iodine availability

39
Q

What are the two main groups of Tyrosine-based hormones?

A

catecholamines and thyroid hormones

40
Q

What are the two main Tryptophan-based hormones?

A

serotonin and melatonin

41
Q

What are the ways in which hormone signaling can be down-regulated?

A
  1. decrease receptor number

2. increase dgradation of the hormone in cells

42
Q

What are the ways in which hormone signalling can be up-regulated?

A
  1. increasing receptor number

2. decreasing intracellular degradation of hormone

43
Q

Where is the receptor for protein/peptide hormones?

A

in the cell membrane of the target cells

44
Q

What kind of kinase are protein hormone receptors often? WHat are the majority though?

A

tyrosine kinase

most activate secondary messengers like GPCRs

45
Q

WHat are three ways these G proteins can transduce signaling cascades?

A
  1. stimualtes adenylate cyclase to produce cAMP
  2. increase cytoplasmic calcium
  3. Activate phospholipase C to produce DAG and IP3
46
Q

Specifically which G protein is usually activated by protein hormones?

A

Gs-alpha

47
Q

What is the signalling pathway for Gs-alpha?

A
  1. activates adenylate cyclase
  2. increases produciton of cAMP
  3. cAMP activates PKA
  4. PKA phosphorylates lots of targets
48
Q

What family are the steroid receptors in?

A

nuclear receptor superfamily

49
Q

Describe the sequence at the binding site for the steroid receptors (the hormnoe binding response element)?

A

it’s a palindrome

50
Q

What are the steroid hormone receptor ligands we care about?

A 
estrogens
progesterones
androgens
glucocorticoids
mineralocorticoids
51
Q

What kind of receptor family is used by thyroid hormone?

A

RXR heterodimers

unliganded RXR binds liganded receptor

52
Q

What is the main substrate in a liganded RXR homodimer system?

A

all trans retinoic acid

53
Q

Describe the transcriptional activation of RXR:TR heterodimer by thyroid hormone.

A
  1. the RXR and TR are bound to the hormone response element with a transcriptional corepressor
  2. transcription co-repressor is released when the T3 binds to the TR
  3. a transcription co-activator binds to the hormone receptor heterodimer complex
  4. transcrpition is modulated
54
Q

Hormones are degraded by liver and kidney metabolism. Speciically what happens to steroid hormones?

A

oxidation by liver cytochrom p450 (phase 1)

55
Q

Why is pulsatile secretion of hypothalamic and pituitary hormones required?

A

prevents desensitiztaion of the downstream hormone receptors

importance because continuous administration of these hormones would down-regulate the hormone receptors and thus reduce hormone signaling

56
Q

What about a sleep cycle will requires adjustment of when to take blood samples to evaluate someones hormone levels?

A

hypothalamic hormone secretion has a circadian rhythm of secretion

57
Q

What does it mean for a hormone to be permissive?

A

it allows another hormone to exert it’s full effect

58
Q

Which would icnrease signalling more - an additive or synergistic relationship?

A

synergistic

ER Week 1 (11 decks)

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