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FHB Exam 4: Endocrinology and Reproduction > Endocrine II: Hormone Properties > Flashcards

Endocrine II: Hormone Properties Flashcards

1
Q

What are some of the characteristics of norepinephrine?

A
  • functions as a NT and hormone (primary function is neurotransmission; most is in synapse)
  • very little released into blood
  • requires SNS stim. for conversion from precursor
  • tissue conc. = that of the synapse
  • dopamine beta-hydroxylase catalyzes rxn
  • symp. post-gang. neurons release NE
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2
Q

What are some of the defining characteristics of dopamine?

A
  • tonic inhibitor of prolactin in anterior pituitary
  • dopaminergic neurons arise from arcuate nucleus in hypothalamus
  • dopamine released into hypophysial capillary bed
  • dopaminergic neurons in arcuate distinct from those in other parts of brain
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3
Q

Which are the 5 amine hormones? Which are catecholamines vs. indoleamines?

A

catecholamines:

  • norepi
  • epi
  • dopamine

indoleamines:

  • serotonin
  • melatonin
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4
Q

___% of serotonin is made in _________ cells in the gut.

A

95; enterochromaffin

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5
Q

Where is melatonin produced?

A

pineal gland

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6
Q

Which enzyme is capable of deactivating catecholamines and indoleamines?

A

monoamine oxidase (MAO)

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7
Q

Most hypothalamic and pituitary hormones belong to which category of hormones?

A

peptides/proteins

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8
Q

Where are the steroid hormones made?

A

placenta, adrenal gland, testes, and ovaries

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9
Q

Which type of hormone is vitamin D considered?

A

steroid hormone (secosteroid)

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10
Q

What are the 5 categories of steroid hormones?

A

glucocorticoids, mineralocorticoids, progestins, androgens, and estrogens

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11
Q

What are some biological examples of positive feedback?

A
  • parturition (childbirth)
  • lactation
  • ovulation
  • blood clotting
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12
Q

Steroid hormones are synthesized from the common precursor, ___________

A

pregnenolone, which is subsequently converted to the 5 different categories of steroid hormones in specific tissues

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13
Q

What are some factors that affect levels of circulating hormones?

A

age, body weight, time of day (Circadian rhythms), sex (M/F), diet

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14
Q

What are the 2 main body organs where dopamine is made?

A

brain and adrenal glands

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15
Q

What is the main hormone action of dopamine?

A

It inhibits prolactin release from the anterior pituitary.

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16
Q

What is the rate-limiting step for catecholamine synthesis?

A

tyrosine hydroxylase

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17
Q

What is the rate-limiting step for conversion of L-DOPA to dopamine?

A

dopamine decarboxylase

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18
Q

What is the rate-limiting step for conversion of dopamine to norepinephrine?

A

dopamine beta-hydroxylase

19
Q

What is the rate-limiting enzyme for indoleamine synthesis?

A

tryptophan hydroxylase (TPH)

20
Q

What is the alternate name for serotonin?

A

5-hydroxytryptamine (5-HT)

21
Q

How is melatonin synthesized?

A

It is converted from serotonin in the pineal gland.

22
Q

What is the rate-limiting enzyme for melatonin synthesis?

A

serotonin N-acetyltransferase (SNA)

23
Q

What is melatonin used therapeutically for?

A

insomnia, jet lag, SAD, migraines, etc.

24
Q

In the process of melatonin secretion, light information is conveyed to the ____ via the __________.

A

SCN; retinohypothalamic tract (RHT)

25
Q

What is the urinary indicator for excessive catecholamine production?

A

VMA (vanillylmandelic acid)

26
Q

What are the two primary mechanisms of monoamine metabolism?

A

1) Oxidative deamination via monoamine oxidase (MAO); inactivates catecholamines and indoleamines
2) Methylation via catechol-o-methyltransferase (COMT); involved in metabolism of catecholamines
3) Decarboxylation via DOPA decarboxylase (DDC); converts L-DOPA to dopamine

27
Q

What are Monoamine Oxidase Inhibitors?

A

They are pharmaceutical drugs used to treat depression and anxiety disorders by preventing the inactivation of catecholamines and indoleamines, many of which are involved with mood.

28
Q

What is the endocrine function of serotonin?

A

Endocrine function is exerted on the gut; it is a vasoconstrictor and stimulates smooth muscle contraction in the intestine

29
Q

What typically determines the half-life of protein/peptide hormones? What is the exception?

A

sizes typically determines HL; exception is when a protein/peptide hormone has a plasma binding protein, which will lengthen HL

30
Q

What is the difference b/t a preprohormone, prohormone, and hormone?

A
  • preprohormone: signal peptide+hormone+copeptides
  • prohormone: copeptides+hormone
  • hormone: cleaved and not associated with any signal peptide or co-peptide; active form
31
Q

What are the 3 chemical categories of hormones?

A
  1. Monoamines (catecholamines, indoleamines)
  2. Peptides/proteins
  3. Steroids
32
Q

Endocrine action of dopamine is from _____ neurons.

A

TIDA (tuberoinfundibular dopamine)

33
Q

Where does conversion of norepi to epi occur?

A

in the adrenal medulla, which is innervated by the splanchnic nerve

34
Q

_______ cells of adrenal medulla are homologous to postsympathetic neurons.

A

chromaffin (conversion of norepi to epi takes place in chromaffin cells, which then release epi into circulation)

35
Q

Explain the derivation of the indoleamines, starting with tryptophan.

A

Tryptophan is converted to serotonin via tryptophan hydroxylase (rate-lim. enzyme); serotonin is converted to melatonin in pineal gland via serotonin N-acetyltransferase.

36
Q

Explain what SSRIs are.

A

Selective Serotonin Reuptake Inhibitors - increase the conc. of serotonin at the synaptic cleft and used to treat depression and other related mental health disorders.

37
Q

How does melatonin affect the reproductive system?

A

It is a POTENT inhibitor of reproduction - causes decreased spermatogenesis and testis size in males.

38
Q

Which functions does melatonin regulate?

A

regulates circadian rhythms of hormones (endocrine), metabolic processes, and behaviors (ie, feeding behavior)

39
Q

What are the inhibitors of DOPA decarboxylase?

A

carbidopa and benserazide (used in Parkinson’s patients)

40
Q

What are the inhibitors of COMT?

A

entacapone (may be used to treat Parkinson’s)

41
Q

What is the function of the signal peptide that is part of the preprohormone?

A

It directs the preprohormone into the ER to undergo further processing/packaging.

42
Q

Where does final cleavage of the co-peptide from the prohormone occur?

A

usually in vesicles

43
Q

What is short loop feedback?

A

pituitary hormone inhibition of hypothalamic hormones

FHB Exam 4: Endocrinology and Reproduction (14 decks)

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