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Endocrinology > Lect. 1 - General Principles > Flashcards

Lect. 1 - General Principles Flashcards

1
Q

three large regulatory systems in mammals that are responsible for the transfer of information between different parts of the organism and participate in maintaining homeostasis in the cells, tissues and entire body:

A

nervous-
immune- &
endocrine systems

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2
Q

Acromegaly is

A

a condition where the body produces too much growth hormone

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3
Q

Endocrinology is

A

the study of chemical communication systems that provide the means to control a huge number of physiologic processes.

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4
Q

Endocrine glands arise during
development from all three embryologic tissue layers:

A

(endoderm, mesoderm, ectoderm).

The type of endocrine product is determined by which tissue layer a gland originated in.

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5
Q

Glands of ectodermal and endodermal origin produce (2)

A

peptide and amine hormones.

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6
Q

Glands of mesodermal-origin secrete hormones based on

A

lipids.

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7
Q

Two major categories of glands in the body

A

Exocrine & endocrine Glands

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8
Q

Exocrine glands have

A

ducts that carry their secretory product to a surface.

These glands include the sweat, sebaceous, and
mammary glands and, the glands that secrete digestive enzymes.

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9
Q

The endocrine glands do not have

A

ducts to carry their product to a surface. They
are called ductless glands.

The secretory products of endocrine glands are called hormones and are secreted
directly into the blood.

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10
Q

Name all “classic” endodrine glands. (8)

A
  • Adrenals
  • Hypothalamus
  • Gonads (ovary, testis)
  • Pancreas (islets of Langerhans)
  • Parathyroid glands
  • Pituitary
  • Pineal gland
  • Thyroid gland
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11
Q

Pineal gland produces?

A

melatonin

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12
Q

Posterior pituitary/neurohypophysis produces?

A

oxytocin and vasopressin/ADH

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13
Q

Anterior pituitary/adenohypophysis produces? (6)

A

Corticotropin (ACTH)
FSH
Growth hormone/somatotropin

LH
Prolactin
Thyrotropin (TSH)

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14
Q

The thyroid gland produces what hormones?

A

triiodothyronine (T3)
thyroxine (T4)
Calcitonin

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15
Q

Parathyroid hormone function?

A

Regulates plasma Ca2+ and phosphate levels.

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16
Q

A hormone the heart produces

A

atrial natriuretic peptide / hormone

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17
Q

2 hormones the liver produces

A

angiotensinogen
insulin-like growth factors

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18
Q

3 hormones produced in the adrenal cortex

A

aldosterone
cortisol
androgens

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19
Q

adrenal medulla produces

A

epinephrine & norepinephrine

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20
Q

hormones produced by the kidneys

A

renin
erythropoietin
1, 25 dihydroxy-vitamin D3 (calcitriol)

Calciferol is a broad term for vitamin D compounds, including D2 and D3.

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21
Q

skin produces what hormone

A

When the skin is exposed to (UVB) radiation from the sun, a compound called 7-dehydrocholesterol, present in the skin, is converted into previtamin D3.

Previtamin D3 is then converted into vitamin D3 (cholecalciferol) through a heat-dependent process.

Vitamin D3 is subsequently metabolized in the liver and kidneys into its active form, calcitriol.

Calcitriol is the same as 1,25 dihydroxy-vitamin D3.

Calciferol is an umbrella term for all D vitamin compounds.

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22
Q

aldosterone broad function?

A

Na+ and K+ homeostasis.

Aldosterone acts on the kidneys, specifically on the cells of the distal tubules and collecting ducts, to enhance the reabsorption of sodium ions.

sodium retention, potassium excretion
Acid-Base Balance

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23
Q

Hormones are complex chemical substances produced by

A

ductless endocrine glands or individual hormone producing cells (incretory glandular cells) that are secreted directly into the bloodstream and act as humoral regulators of the organism.

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24
Q

Neuroendocrine signaling:

A

Neurosecretory neurons release neurohormones into the circulatory system

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25
Q

define autocrine regulation

A

Cells release local regulators that
regulate the same cells that produced it.

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26
Q

define paracrine regulation

A

Cells release local regulators that
diffuse through extracellular fluid to regulate nearby cells

example: insulin-like growth factor 1 (IGF-1)

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27
Q

The target cell hormone receptors have two main functions:

A

(1) to recognize and bind with high affinity to their particular hormones

(2) to initiate a signal to appropriate intracellular effectors

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28
Q

up-regulation =
down-regulation =

A

an increase and decrease in hormone receptors

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29
Q

Sensitivity is related to

A

the number of receptors which are constantly
being synthesized and degraded.

Physiological conditions affect receptor
number and affinity (pH, temp. ion concent. etc.).

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30
Q

What is the GH IGF-1 axis?
What is the relationship between GH and IGF-1?

A

The growth hormone (GH)–insulin-like growth factor (IGF)-I axis is the principle endocrine system regulating linear growth in children.

GH induces the generation of insulin-like growth factor 1 (IGF-1, also called somatomedin 1) in the liver and regulates the paracrine production of IGF-1 in many other tissues. The cascade of the growth hormone axis.

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31
Q

Target cell activation depends on 3 factors:

A
  • Levels of the hormone
  • Relative number of receptors on the target cell
  • Affinity of those receptors for the hormone
32
Q

Agonists are

A

molecules that bind to the receptor and induce all the post-receptor events that lead to a biologic effect.

33
Q

Antagonists are

A

molecules that bind to the receptor and block binding of the agonist, but fail to trigger intracellular signalling events.

34
Q

Example of a Progesterone receptor agonist

A

Megestrol acetate is used in dogs and in cats to control heat cycles (estrus) and in bitches to treat false pregnancy.

35
Q

Example of a Progesterone receptor antagonist

A

Aglepristone (Alizin)

Effective on uterine progesterone receptors, with a binding affinity three times stronger than endogenous progesterone, providing effective competitive antagonism thus blocking progesterone which is responsible for implantation and pregnancy maintenance.

36
Q

Cortisol (adrenal cortex) acts on the
hypothalamus/anterior pituitary gland to inhibit

A

ACTH / adrenocorticotropic hormone

This is an example of negative autoregulation.

37
Q

Testosterone (testis) acts on the
hypothalamus/anterior pituitary gland to inhibit

A

testosterone is part of a negative feedback mechanism that inhibits GnRH release by the hypothalamus and LH release by the pituitary.

38
Q

Oestradiol (ovary) acts of the
hypothalamus/anterior pituitary gland to stimulate

A

luteinizing hormone (LH)

This is an example of positive autoregulation.

39
Q

define Circadian

A

24 hour cycle
(circa = about; dies = day)

40
Q

define Ultradian

A

a cycle shorter than 24 hours

41
Q

define Infradian

A

a cycle that is longer than 24 hours
(i.e. 21 day estrous cycle in cows)

42
Q

hormones can chemically be: (name 5 substances)

A

amino acids
fatty acids
peptides
proteins
steroids (lipid based)

43
Q

melatonin is derived from

A

the essential amino acid, tryptophan

44
Q

catecholamines (apinephrine and dopamine), and thyroid hormones are derived from?

A

the non essential amino acid tyrosine

45
Q

Tyrosine is the parent amino acid for (2)

A

catecholamines &
thyroid hormones

46
Q

Catecholamines are made by modifying ?

A

the side groups of tyrosine

47
Q

Thyroid hormones are synthesized from

A

2 tyrosines and iodine atoms

48
Q

name Lipid-Derived Hormones

A

steroids such as testosterone and estradiol,
progesterone, cortisol, aldosterone

49
Q

Most lipid hormones are derived from

A

cholesterol and thus are structurally similar to it.

Chemically, these hormones are usually
ketones or alcohols; their chemical names will end in “-ol” for alcohols or “-one” for ketones.

e.g. estradiol and testosterone

50
Q

Typically, endocrinologists classify steroid hormones into five groups of molecules, based primarily on the receptor to which they bind. Name the groups.

A

Androgens (testosterone)
Estrogens (estradiol)

Glucocorticoids (ie. cortisol)

Mineralocorticoids (aldosterone)
Progestogen/progestins (progesterone)

51
Q

Following secretion, all steroids

A

bind to some extent to plasma proteins.

This binding is often low affinity and non-specific (e.g. to albumin), but some steroids are transported by specific binding proteins, which clearly affects their halflife and rate of elimination.

52
Q

Prostaglandins, prostacyclins, leukotrienes and thromboxanes are derived from

A

fatty acids

Arachadonic acid is the most abundant precursor for these hormones.

53
Q

Prostaglandins tyicpically act where in respect to location of release

A

Prostaglandins are local hormones but
prostaglandin F2α (PGF2α) can also act
as a blood borne hormone.

54
Q

Many hormones are polypeptides, but most are

A

proteins.

55
Q

Explain regulated secretion of peptide hormones.

A

The cell stores hormone in secretory granules and releases them in “bursts” when stimulated. This is the most commonly used pathway and allows cells to secrete a large amount of hormone over a short period of time.

e.g. GH

56
Q

Explain Constitutive secretion of peptide hormones.

A

The cell does not store hormone, but secretes it from secretory vesicles as it is synthesized.

e.g. FSH

57
Q

2 functions for hormones binding to specific binding proteins

A
  • (i) increase the solubility of hydrophobic hormones
  • (ii) protect the hormone from rapid metabolism by proteolytic enzymes in blood
58
Q

Peptide or protein hormones (pituitary, hypothalamic, and parathyroid hormones; and insulin) are water soluble and circulate mostly how?

A

in free (unbound) forms.

59
Q

how do Insulin-like growth factor (IGF) and Growth hormone travel?

A

IGF has 6 carrier proteins.

Growth hormone has also carrier proteins.

60
Q

Water-soluble hormones generally have a short half-life because

A

they are catabolized by circulating enzymes.

For example, insulin has a halflife of 3 to 5 minutes and is catabolized by insulinases.

61
Q

Lipid-soluble hormones, such as cortisol and adrenal androgens, are transported how?

A

bound to a carrier or transport protein and
can remain in the blood for hours to days.

62
Q

what can free hormones do that bound can’t

A

signal a target cell.

63
Q

Because an equilibrium exists between the concentrations of free hormones and hormones bound to plasma proteins, a significant change
in the concentration of binding proteins can affect

A

the concentration of free hormones in the plasma.

64
Q

The principal steroid binding proteins in
plasma are

A

albumin,
corticosteroid binding globulin (CBG, transcortin),

sex-hormone binding globulin (SHBG) which
is also known as testosterone-estradiol-binding globulin (TeBG).

65
Q

The effect of hormone on the tissue is determined by:

A
  • Hormone concentration in blood
  • Presence of hormone receptors and post-receptor mechanisms
66
Q

all hormone receptors can be categorized into one of two types, based on

A

their location within the cell:
cell surface receptors or
intracellualr receptors

67
Q

Principle Mechanism of action for cell surface receptors

A

Generation of second messengers which alter the
activity of other molecules - usually enzymes - within the cell.

68
Q

Principle Mechanism of action for intraceluular receptors

A

Alter transcriptional activity of responsive genes.

69
Q

Group-I hormones are

A

Fat-soluble hormones (steroid hormones) that are hydrophobic or lipophilic. They are synthesised from cholesterol and thus classified under Group-I hormones.

The Group-I hormones quickly diffuse in the plasma membrane, reach the cytosol where they can bind the intracellular receptor.

70
Q

The Group-II hormones bind to

A

the extracellular domain of the cell receptors present on the plasma membrane

71
Q

an example of a secondary messenger

A

adenylyl cyclase

72
Q

What is JAK-STAT

A

JAK: “just another kinase”
STAT: signal transducers and activators of
transcription.

a family of signal transducer molecules

73
Q

explain Pseudohypoparathyroidism shortly

A

impairment in ability to regulate Ca+ & Phos homeostasis.

PTH is produced in normal amounts but is unabe to prodduce effect due to a defect in the signal transduction pathway, adenyl cyclase is not activated.

resistance or unresponsiveness to parathyroid hormone

74
Q

The time between hormone pulse intervals can range from

A

minutes to hours

75
Q

Rceptor recognition and binding is followed by what 3 broad steps:

A

signal transduction,,
phosphorylation &
intracellular pathway activation

76
Q

tropic versus trophic

A

Tropic hormones are released by an endocrine gland and act upon another endocrine gland (e.g. thyrotropin).

Trophic hormones stimulate growth in target tissues (e.g. GH).

Note: All the tropic hormones of the anterior lobe are simultaneously trophic hormones, in whose absence their target glands atrophy.

Endocrinology (16 decks)

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