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[OS 202] C > Introduction to Endocrine Physiology > Flashcards

Introduction to Endocrine Physiology Flashcards

1
Q

True or False: Hormones are produced by organs.

A

False - hormones can be produced by individual cells

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2
Q

True or False: Hormones must be released into the blood stream.

A

False - there is paracrine/autocrine signaling, chemical mediators may be diffused into the interstitial space

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3
Q

True or False: Hormones exert its specific function.

A

True. (hehehe)

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4
Q

What are the types of hormones according to structure?

A
  • amino acid derivatives/amines
  • proteins, peptides, and glycoproteins
  • steroids - prostanoids/prostaglandins
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5
Q

Enumerate the amino acid/amine hormones

A
  • thyroid homones
  • catecholamines
  • melatonin
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6
Q

How are thyroid hormones synthesized?

A

Iodination of benzene ring of tyrosine

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7
Q

Give examples of thyroid hormones.

A
  • T3 or triiodothyronine
  • T4 or thyroxine
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8
Q

How are catecholamines synthesized?

A

Introduction of a second hydroxyl group in the benzene ring of tyrosine

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9
Q

Give examples of catecholamines.

A

norepinephrine, epinephrine, dopamine

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10
Q

How is melatonin synthesized?

A

Acetylation of the aliphatic amino group and hydroxylation of the indole ring of tryptophan

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11
Q

Enumerate the protein/glycoprotein hormones

A
  • thyrotropin-releasing hormone (TRH), growth hormone (GH), and luteinizing hormone (LH)
  • insulin
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12
Q

What is peculiar about TRH, GH, and LH?

A

They all come from a common ancestral gene; they have similar basic structures but with different functions

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13
Q

What is the smallest hormone? Where is it produced?

A

TRH (3 amino acids), produced in the hypothalamus

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14
Q

What is peculiar about insulin production?

A

Analogues (from alternative splicing and post-translational modification) of insulin produce slightly different effects. This is significant for some patients that are resistant to certain types of insulin

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16
Q

Enumerate the steroid hormones

A
  • cortisol - glucocorticoid - aldosterone - mineralocorticoid - DHEA-S, androstenedione - sex hormones - vitamin D metabolites
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17
Q

How are steroids produced?

A

Cholesterol undergoes modification of side chains, hydroxylation, and ring formation.

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18
Q

How are prostanoids or prostaglandins produced?

A

addition of oxygen atoms and cyclization of arachidonic acid

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19
Q

How are peptide and steroid hormones stored?

A

Peptide hormones are usually stored in granules, while steroids are usually free in the cytoplasm

20
Q

How are peptide and steroid hormones transported in the blood?

A

Peptide hormones are usually free (faster action), while steroids are usually bound to transport proteins.

21
Q

What are the types of hormones according to mechanism of action?

A
  • hormones that bind to intracellular receptors (i.e. lipophilic hormones)
  • hormones that bind to cell-surface receptors
22
Q

How are hormones classified according to function?

A
  • reproduction
  • growth and development
  • homeostasis
  • energy availability
23
Q

Types of cell-to-cell interactions:

A
  • autocrine (short distance to cells of the same type)
  • paracrine (short distance to cells of different type)
  • endocrine (long distance via blood stream)
  • neurocrine (long distance via blood stream produced by a nerve cell)
24
Q

preprohormone vs prohormone vs hormone

A
  • preprohormone - produced in ribosomes; signal peptide is still attached
  • prohormone - produced in RER; signal peptide is cleaved off
  • hormone - produced in Golgi apparatus; copeptide is cleaved off; stored in granules
25
Q

examples of special precursor molecules:

A
  • propiomelanocortin (POMC) - precursor for ACTH (adenocorticotropic hormone)
  • glucagon precursor - precursor for glucagon (pancreas) or glucagon-like peptide (GLP, in L cells of intestine)
26
Q

Types of hormone release

A
  • vesicular e.g. proteins, peptides, and catecholamines (stored in granules)
  • non-vesicular e.g. steroids and eicosanoids (lipophilic hormones), diffuse across plasma membrane out of the cell
  • hybrid (combination) e.g. thyroid hormones
27
Q

How are non-vesicular hormones protected from degradation?

A

by being bound to transport proteins e.g. thyroglobulin for thyroid hormones and cortisol-binding protein for cortisol

28
Q

mechanism of peptide hormone release

A

Stimulus-secretion coupling
1. Stimulus (depends on hormone)
2. Activation of second messenger (only for some).
3. Increase in intracellular calcium drives contraction of microtubules
and microfilaments attached to secretory granules
4. Bring secretory granules to cell membrane
5. Granule fuses with cell membrane
6. Hormone is released (exocytosis).

29
Q

How are steroids transported?

A

Steroids are bound to transport proteins, to protect them from metabolism and renal clearance (wastage)

30
Q

How are peptide hormones transported?

A

Free - short-lived, destroyed by circulating proteases, have immediate effect

31
Q

protein hormones that are bound to carrier protein:

A

GH and IGF-1

32
Q

Cells that eventually receive the hormone in circulation

A

target cells

33
Q

specialized structure that will bind a particular hormone

A

receptor

34
Q

Parts of the receptor

A
  • recognition domain - binds to the hormone
  • coupling domain - involved in signal transduction; intracellular, mediates signaling of receptor
35
Q

three conditions for hormone to produce an effect

A
  1. Hormone must be recognized by receptor.
  2. Hormone-Receptor Complex must have the ability to produce signal
    generation     in cytoplasm/nucleus.
  3. There must be available effector proteins/enzymes and other
    machinery to manifest response.
36
Q

Will there be an effect if receptor is weakly bound to a homologue of the original hormone?

A

Yes, and the effects are those produced by the original hormone.

37
Q

Significance of Human Chorionic Gonadotropin (HCG)

A
  • structural homologue of TSH (thyroid-stimulating hormone) and LH (luteinizing hormone)
  • released during pregnancy by placenta
  • may activate thyroid hormones
  • causes gestational transient thyrotoxicosis associated with hyperemesis gravidarum (morning sickness)
38
Q

Hormone mechanisms of action

A
  • G-protein-linked receptors
  • G-protein second messengers
  • enzyme-linked receptors
39
Q

How many subunits are there in a G-protein? Enumerate:

A

three: alpha, beta, and gamma

40
Q

What are the functions of the subunits of G-proteins?

A

alpha-subunit - binds to receptors, to effector molecules, and to GDP and GTP

beta-gamma-subunit (dimer) - may serve to attach the G-protein to the plasma membrane

41
Q

What are the basic components of a G-protein pathway?

A
  • Receptor
  • G-protein complex
  • Target enzyme or channel
42
Q

Cation required for the G-protein cycle

A

Mg2+

43
Q

What are the main effector systems used by G-proteins?

A
  • adenylyl cyclase-cAMP system
  • plasma membrane phospholipids/phospholipase C pathway
  • calcium-calmodulin system
44
Q

What does the adenylyl cyclase-cAMP system do?

A

It catalyzes the formation of cAMP from ATP with Mg2+ as cofactor. This increases the intracellular cAMP levels.

[OS 202] C (1 decks)

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