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FHB Exam 4 > Endocrine 2: basics > Flashcards

Endocrine 2: basics Flashcards

1
Q

What are the chemical categories of hormones?

A
  • monoamines (catecholamines and indolamines)
  • peptides/proteins
  • steroids
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2
Q

Characterize monoamines.

A
  • short half life
  • transported freely in the blood
  • bind to surface membrane receptor and activate second messenger signaling cascade
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3
Q

What is the most common chemical composition of hormones?

A
  • peptides/proteins
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4
Q

List hormone categories in order of their half-life (short to long).

A
  • monoamines
  • peptides/proteins
  • steroids
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5
Q

What is the main difference between catecholamines and indolamines?

A
  • catecholamines are derived from tyrosine via tyrosine hydroxylase
  • indolamines are derived from tryptophan via tryptophan hydroxylase
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6
Q

Describe the enzymatic reaction that forms catecholamines.

A

tyrosine => tyrosine hydroxylase => L-DOPA => dopamine => norepi/epi

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7
Q

What is the rate limiting step for all catecholamine formation?

A

tyrosine hydroxylase

- used as biomarker of dopaminergic activity

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8
Q

What is unique about catecholamines?

A

act as hormone and neurotransmitter

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9
Q

Where is dopamine produced?

A

Brain

  • arcuate nucleus (tonically express TH; unaffected by Parkinson’s; released to anterior pituitary)
  • substantia nigra/ventral tegmental area (affected by Parkinson’s)

Adrenal Medulla
- converted to norepi/epi via dopamine beta-hydroxylase

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10
Q

What is the function of dopamine?

A
  • arcuate nucleus => hypophysial capillary bed (bloodstream) => pituitary gland => inhibits prolactin release
  • reward centers, mood in the brain
  • conversion to norepi/epi
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11
Q

What are the functions of norepinephrine?

A
  • function as neurotransmitter and hormone
  • requires sympathetic stimulation
  • conversion from dopamine takes place in neurons
  • dopamine => dopamine beta-hydroxylase => norepinephrine
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12
Q

Describe the 2 mechanisms of sympathetic norepinephrine release.

A
  1. preganglionic neuron => ACh on nicotinic receptors => postganglionic neuron => norepi on alpha and beta adrenergic receptors
  2. preganglionic neuron (splanchnic) => ACh on chromaffin cells in adrenal medulla => make dopamine => converted to norepi/epi => epi mainly released
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13
Q

List catecholamines.

A

dopamine
norepinephrine
epinephrine

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14
Q

List indolamines.

A

serotonin

melatonin

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15
Q

Characterize indolamines.

A
  • rate limiting step is tryptophan hydroxylase
  • serotonin is both neurotransmitter and hormone
  • melatonin is a hormone produced by pineal gland
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16
Q

Describe serotonin.

A
  • both neurotransmitter and hormone
  • aka 5-hydroxytryptamine (5-HT)
  • majority is produced in the gut
  • acts as vasoconstrictor and smooth muscle contractions in the gut
  • happiness hormone
17
Q

Describe the use of SSRIs.

A
  • Selective Serotonin Reuptake Inhibitors
  • block reuptake proteins on the terminal end of releasing neurons
  • causes increase of serotonin remaining in the synaptic cleft to increase duration of action
  • used to treat mental health disorders
18
Q

What are some clinical considerations of SSRIs?

A
  • receiving neuron will downregulate serotonin receptors
  • negative feedback will cause releasing neuron to downregulate serotonin production
  • not effective in most patients
19
Q

How is melatonin produced?

A

serotonin => N-acetyltransferase (SNA) => melatonin

  • SNA is rate limiting enzyme
  • most actively produced at night
  • made in pineal gland
20
Q

How is melatonin used clinically? What are some clinical considerations?

A
  • used to treat insomnia, jet lag, SAD, migraines

- inhibits reproduction => decreased testosterone and testis size in males

21
Q

Describe how melatonin secretion is regulated.

A

Requires prolonged hours of darkness to reach maximum activity
- light => retinohypothalamic tract => SCN => pineal gland => regulates circadian rhythms

22
Q

Describe protein hormone processing.

A
  1. after transcription/etc = preprohormone = signal (to ER), hormone, and copeptide
  2. after translation = signal diverts it to the ER => signal degraded
  3. prohormone = hormone + copeptide
  4. cleavage and packaging => hormone = active form; copeptide can have other effects
23
Q

What is the relationship between peptide composition and half life? What is the exception?

A

In general, the shorter the peptide hormone, the shorter the half-life
- IGF1 has a long half-life because it is bound to protein in plasma

24
Q

List the steroid hormones made in the following organs:

  • adrenal cortex
  • kidney
  • placenta
  • testis
  • ovary
A
  • adrenal cortex = cortisol, mineralcorticoids, DHEA, androstenedione
  • kidney = vitamin D
  • placenta = progesterone, estriol
  • testis = testosterone
  • ovary = 17D-estradiol, progesterone
25
Q

Describe cholesterol derivative synthesis in the adrenal gland.

A
  1. cholesterol enters the inner mitochondria via StAR protein, which also houses P450scc, an enzyme that converts cholesterol to pregnenolone
  2. defects in StAR/P450scc is embryonic lethal
26
Q

What is an endocrine axis?

A

3-tier

  1. hypothalamus
  2. pituitary
  3. peripheral organ
27
Q

Describe endocrine axis negative feedback.

A
  • short loop = pituitary hormone will negatively feedback on to the hypothalamus
  • long loop = peripheral endocrine hormone will negatively feedback on the pituitary and/or hypothalamus
28
Q

Describe physiological driven negative feedback.

A

There is no hormone released by the target organ. Instead, there is a change in the physiological state that immediately causes cessation of hormone production.

29
Q

List examples of positive feedback.

A
  1. oxytocin during childbirth
  2. oxytocin during suckling
  3. LH => estradiol in developing follicle => more LH => oocyte released
  4. blood clotting via platelets at site of tissue injury
30
Q

List factors that affect “normal” circulating hormone levels.

A
  • sex
  • age
  • time of day
  • weight
  • diet
31
Q

How do certain hormones change with age?

A
  • catecholamines and glucocorticoids increase with age
  • testosterone increases during puberty and decreases with age
  • estrogen sharply increases during puberty and sharply declines during menopause
  • androgens peak at mid-20s and then decrease with age
32
Q

Describe “normal” circulating ANP/BNP and the factors that contribute to it.

A 
Sex
- men range = 4-40
- women range = 8-80 (doubled)
Weight - decreased in obese pts
Age - increases with age
  • used to rule out congestive heart failure (BNP - b/c longer half-life)
  • elevated in heart and renal failure
33
Q

Describe monoamine metabolism.

A 
MonoAmine Oxidase (MAO) - oxidative deamination removes an amine group => aldehyde and ammonia => Aldehyde Dehydrogenase (AD) => further metabolizes aldehyde
- inactivates both catecholamines and indolamines

Catechol-O-MethylTransferase (COMT) - adds methyl group to catecholamines only

34
Q

What is the clinical use of monoamine metabolism?

A
  • MAOIs inhibit catecholamine metabolism => longer duration of action (used in depression to increase activity of dopamine)
35
Q

Define DHPG.

A
  • primary metabolite of catecholamines found in extraneural tissue
36
Q

Define VMA.

A

VanillylMandelic Acid

  • urinary indicator of excessive catecholamine production
  • used to diagnose catecholamine producing tumors
  • end metabolite of catecholamine metabolism

FHB Exam 4 (16 decks)

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